diff --git a/doc/whats_new/v0.7.rst b/doc/whats_new/v0.7.rst
index 6018cc5c4..a9bfc9552 100644
--- a/doc/whats_new/v0.7.rst
+++ b/doc/whats_new/v0.7.rst
@@ -19,6 +19,9 @@ Maintenance
 - Remove `FutureWarning` issued by `scikit-learn` 0.23.
   :pr:`710` by :user:`Guillaume Lemaitre <glemaitre>`.
 
+- Impose keywords only argument as in `scikit-learn`.
+  :pr:`721` by :user:`Guillaume Lemaitre <glemaitre>`.
+
 Changed models
 ..............
 
@@ -63,3 +66,7 @@ Deprecation
   :class:`imblearn.under_sampling.ClusterCentroids` since it was used by
   :class:`sklearn.cluster.KMeans` which deprecated it.
   :pr:`710` by :user:`Guillaume Lemaitre <glemaitre>`.
+
+- Deprecation of passing keyword argument by position similarly to
+  `scikit-learn`.
+  :pr:`721` by :user:`Guillaume lemaitre <glemaitre>`.
diff --git a/imblearn/base.py b/imblearn/base.py
index e66738a45..86bb53778 100644
--- a/imblearn/base.py
+++ b/imblearn/base.py
@@ -14,6 +14,7 @@
 
 from .utils import check_sampling_strategy, check_target_type
 from .utils._validation import ArraysTransformer
+from .utils._validation import _deprecate_positional_args
 
 
 class SamplerMixin(BaseEstimator, metaclass=ABCMeta):
@@ -213,7 +214,8 @@ class FunctionSampler(BaseSampler):
 
     _sampling_type = "bypass"
 
-    def __init__(self, func=None, accept_sparse=True, kw_args=None,
+    @_deprecate_positional_args
+    def __init__(self, *, func=None, accept_sparse=True, kw_args=None,
                  validate=True):
         super().__init__()
         self.func = func
diff --git a/imblearn/combine/_smote_enn.py b/imblearn/combine/_smote_enn.py
index 92e30e32e..74ca81b9c 100644
--- a/imblearn/combine/_smote_enn.py
+++ b/imblearn/combine/_smote_enn.py
@@ -15,6 +15,7 @@
 from ..utils import Substitution
 from ..utils._docstring import _n_jobs_docstring
 from ..utils._docstring import _random_state_docstring
+from ..utils._validation import _deprecate_positional_args
 
 
 @Substitution(
@@ -85,8 +86,10 @@ class SMOTEENN(BaseSampler):
 
     _sampling_type = "over-sampling"
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         sampling_strategy="auto",
         random_state=None,
         smote=None,
diff --git a/imblearn/combine/_smote_tomek.py b/imblearn/combine/_smote_tomek.py
index 078319da0..f8bbb567b 100644
--- a/imblearn/combine/_smote_tomek.py
+++ b/imblearn/combine/_smote_tomek.py
@@ -16,6 +16,7 @@
 from ..utils import Substitution
 from ..utils._docstring import _n_jobs_docstring
 from ..utils._docstring import _random_state_docstring
+from ..utils._validation import _deprecate_positional_args
 
 
 @Substitution(
@@ -85,8 +86,10 @@ class SMOTETomek(BaseSampler):
 
     _sampling_type = "over-sampling"
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         sampling_strategy="auto",
         random_state=None,
         smote=None,
diff --git a/imblearn/datasets/_imbalance.py b/imblearn/datasets/_imbalance.py
index f761a79e8..b10ec3b57 100644
--- a/imblearn/datasets/_imbalance.py
+++ b/imblearn/datasets/_imbalance.py
@@ -9,10 +9,12 @@
 
 from ..under_sampling import RandomUnderSampler
 from ..utils import check_sampling_strategy
+from ..utils._validation import _deprecate_positional_args
 
 
+@_deprecate_positional_args
 def make_imbalance(
-    X, y, sampling_strategy=None, random_state=None, verbose=False, **kwargs
+    X, y, *, sampling_strategy=None, random_state=None, verbose=False, **kwargs
 ):
     """Turns a dataset into an imbalanced dataset with a specific sampling
     strategy.
diff --git a/imblearn/datasets/_zenodo.py b/imblearn/datasets/_zenodo.py
index 3a180ad78..e8a53423a 100644
--- a/imblearn/datasets/_zenodo.py
+++ b/imblearn/datasets/_zenodo.py
@@ -57,6 +57,8 @@
 from sklearn.utils import Bunch
 from sklearn.utils import check_random_state
 
+from ..utils._validation import _deprecate_positional_args
+
 URL = (
     "https://zenodo.org/record/61452/files/"
     "benchmark-imbalanced-learn.tar.gz"
@@ -101,7 +103,9 @@
     MAP_ID_NAME[v + 1] = k
 
 
+@_deprecate_positional_args
 def fetch_datasets(
+    *,
     data_home=None,
     filter_data=None,
     download_if_missing=True,
diff --git a/imblearn/datasets/tests/test_imbalance.py b/imblearn/datasets/tests/test_imbalance.py
index 4c0893521..58612034d 100644
--- a/imblearn/datasets/tests/test_imbalance.py
+++ b/imblearn/datasets/tests/test_imbalance.py
@@ -32,14 +32,14 @@ def test_make_imbalance_error(iris, sampling_strategy, err_msg):
     # cover in the common tests so we will repeat it here
     X, y = iris
     with pytest.raises(ValueError, match=err_msg):
-        make_imbalance(X, y, sampling_strategy)
+        make_imbalance(X, y, sampling_strategy=sampling_strategy)
 
 
 def test_make_imbalance_error_single_class(iris):
     X, y = iris
     y = np.zeros_like(y)
     with pytest.raises(ValueError, match="needs to have more than 1 class."):
-        make_imbalance(X, y, {0: 10})
+        make_imbalance(X, y, sampling_strategy={0: 10})
 
 
 @pytest.mark.parametrize(
diff --git a/imblearn/ensemble/_bagging.py b/imblearn/ensemble/_bagging.py
index a17036306..79916f43a 100644
--- a/imblearn/ensemble/_bagging.py
+++ b/imblearn/ensemble/_bagging.py
@@ -18,6 +18,7 @@
 from ..utils import Substitution, check_target_type, check_sampling_strategy
 from ..utils._docstring import _n_jobs_docstring
 from ..utils._docstring import _random_state_docstring
+from ..utils._validation import _deprecate_positional_args
 
 
 @Substitution(
@@ -175,10 +176,12 @@ class BalancedBaggingClassifier(BaggingClassifier):
      [  2 225]]
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
         base_estimator=None,
         n_estimators=10,
+        *,
         max_samples=1.0,
         max_features=1.0,
         bootstrap=True,
diff --git a/imblearn/ensemble/_easy_ensemble.py b/imblearn/ensemble/_easy_ensemble.py
index 699f1fc94..443ae0d1f 100644
--- a/imblearn/ensemble/_easy_ensemble.py
+++ b/imblearn/ensemble/_easy_ensemble.py
@@ -17,6 +17,7 @@
 from ..utils import Substitution, check_target_type, check_sampling_strategy
 from ..utils._docstring import _n_jobs_docstring
 from ..utils._docstring import _random_state_docstring
+from ..utils._validation import _deprecate_positional_args
 from ..pipeline import Pipeline
 
 MAX_INT = np.iinfo(np.int32).max
@@ -125,10 +126,12 @@ class EasyEnsembleClassifier(BaggingClassifier):
      [  2 225]]
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
         n_estimators=10,
         base_estimator=None,
+        *,
         warm_start=False,
         sampling_strategy="auto",
         replacement=False,
diff --git a/imblearn/ensemble/_forest.py b/imblearn/ensemble/_forest.py
index 0272629ee..cb2b77dc9 100644
--- a/imblearn/ensemble/_forest.py
+++ b/imblearn/ensemble/_forest.py
@@ -34,6 +34,7 @@
 from ..utils._docstring import _n_jobs_docstring
 from ..utils._docstring import _random_state_docstring
 from ..utils._validation import check_sampling_strategy
+from ..utils._validation import _deprecate_positional_args
 
 MAX_INT = np.iinfo(np.int32).max
 
@@ -297,9 +298,11 @@ class labels (multi-output problem).
     [1]
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
         n_estimators=100,
+        *,
         criterion="gini",
         max_depth=None,
         min_samples_split=2,
diff --git a/imblearn/ensemble/_weight_boosting.py b/imblearn/ensemble/_weight_boosting.py
index 177a8cd02..483f14a8a 100644
--- a/imblearn/ensemble/_weight_boosting.py
+++ b/imblearn/ensemble/_weight_boosting.py
@@ -12,6 +12,7 @@
 from ..pipeline import make_pipeline
 from ..utils import Substitution, check_target_type
 from ..utils._docstring import _random_state_docstring
+from ..utils._validation import _deprecate_positional_args
 
 
 @Substitution(
@@ -120,9 +121,11 @@ class RUSBoostClassifier(AdaBoostClassifier):
     array([...])
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
         base_estimator=None,
+        *,
         n_estimators=50,
         learning_rate=1.0,
         algorithm="SAMME.R",
diff --git a/imblearn/keras/_generator.py b/imblearn/keras/_generator.py
index 39f036713..bb241cf6c 100644
--- a/imblearn/keras/_generator.py
+++ b/imblearn/keras/_generator.py
@@ -41,16 +41,17 @@ def import_from_tensforflow():
 
 ParentClass, HAS_KERAS = import_keras()
 
-from scipy.sparse import issparse
+from scipy.sparse import issparse  # noqa
 
-from sklearn.base import clone
-from sklearn.utils import _safe_indexing
-from sklearn.utils import check_random_state
+from sklearn.base import clone  # noqa
+from sklearn.utils import _safe_indexing  # noqa
+from sklearn.utils import check_random_state  # noqa
 
-from ..under_sampling import RandomUnderSampler
-from ..utils import Substitution
-from ..utils._docstring import _random_state_docstring
-from ..tensorflow import balanced_batch_generator as tf_bbg
+from ..under_sampling import RandomUnderSampler  # noqa
+from ..utils import Substitution  # noqa
+from ..utils._docstring import _random_state_docstring  # noqa
+from ..tensorflow import balanced_batch_generator as tf_bbg  # noqa
+from ..utils._validation import _deprecate_positional_args  # noqa
 
 
 class BalancedBatchGenerator(*ParentClass):
@@ -130,10 +131,12 @@ class BalancedBatchGenerator(*ParentClass):
     # flag for keras sequence duck-typing
     use_sequence_api = True
 
+    @_deprecate_positional_args
     def __init__(
         self,
         X,
         y,
+        *,
         sample_weight=None,
         sampler=None,
         batch_size=32,
@@ -199,9 +202,11 @@ def __getitem__(self, index):
 
 
 @Substitution(random_state=_random_state_docstring)
+@_deprecate_positional_args
 def balanced_batch_generator(
     X,
     y,
+    *,
     sample_weight=None,
     sampler=None,
     batch_size=32,
diff --git a/imblearn/metrics/_classification.py b/imblearn/metrics/_classification.py
index 1f48bbda1..3b8dc7256 100644
--- a/imblearn/metrics/_classification.py
+++ b/imblearn/metrics/_classification.py
@@ -30,10 +30,14 @@
 except ImportError:
     from sklearn.externals.funcsigs import signature
 
+from ..utils._validation import _deprecate_positional_args
 
+
+@_deprecate_positional_args
 def sensitivity_specificity_support(
     y_true,
     y_pred,
+    *,
     labels=None,
     pos_label=1,
     average=None,
@@ -279,9 +283,11 @@ def sensitivity_specificity_support(
     return sensitivity, specificity, true_sum
 
 
+@_deprecate_positional_args
 def sensitivity_score(
     y_true,
     y_pred,
+    *,
     labels=None,
     pos_label=1,
     average="binary",
@@ -382,9 +388,11 @@ def sensitivity_score(
     return s
 
 
+@_deprecate_positional_args
 def specificity_score(
     y_true,
     y_pred,
+    *,
     labels=None,
     pos_label=1,
     average="binary",
@@ -485,9 +493,11 @@ def specificity_score(
     return s
 
 
+@_deprecate_positional_args
 def geometric_mean_score(
     y_true,
     y_pred,
+    *,
     labels=None,
     pos_label=1,
     average="multiclass",
@@ -675,7 +685,8 @@ class is unrecognized by the classifier, G-mean resolves to zero. To
         return gmean
 
 
-def make_index_balanced_accuracy(alpha=0.1, squared=True):
+@_deprecate_positional_args
+def make_index_balanced_accuracy(*, alpha=0.1, squared=True):
     """Balance any scoring function using the index balanced accuracy
 
     This factory function wraps scoring function to express it as the
@@ -785,9 +796,11 @@ def compute_score(*args, **kwargs):
     return decorate
 
 
+@_deprecate_positional_args
 def classification_report_imbalanced(
     y_true,
     y_pred,
+    *,
     labels=None,
     target_names=None,
     sample_weight=None,
diff --git a/imblearn/over_sampling/_adasyn.py b/imblearn/over_sampling/_adasyn.py
index f014243e7..60b1acc1f 100644
--- a/imblearn/over_sampling/_adasyn.py
+++ b/imblearn/over_sampling/_adasyn.py
@@ -15,6 +15,7 @@
 from ..utils import Substitution
 from ..utils._docstring import _n_jobs_docstring
 from ..utils._docstring import _random_state_docstring
+from ..utils._validation import _deprecate_positional_args
 
 
 @Substitution(
@@ -81,8 +82,10 @@ class ADASYN(BaseOverSampler):
     Resampled dataset shape Counter({{0: 904, 1: 900}})
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         sampling_strategy="auto",
         random_state=None,
         n_neighbors=5,
diff --git a/imblearn/over_sampling/_random_over_sampler.py b/imblearn/over_sampling/_random_over_sampler.py
index 4a2cfbf71..cbdaf2179 100644
--- a/imblearn/over_sampling/_random_over_sampler.py
+++ b/imblearn/over_sampling/_random_over_sampler.py
@@ -14,6 +14,7 @@
 from ..utils import check_target_type
 from ..utils import Substitution
 from ..utils._docstring import _random_state_docstring
+from ..utils._validation import _deprecate_positional_args
 
 @Substitution(
     sampling_strategy=BaseOverSampler._sampling_strategy_docstring,
@@ -68,7 +69,8 @@ class RandomOverSampler(BaseOverSampler):
     Resampled dataset shape Counter({{0: 900, 1: 900}})
     """
 
-    def __init__(self, sampling_strategy="auto", random_state=None):
+    @_deprecate_positional_args
+    def __init__(self, *, sampling_strategy="auto", random_state=None):
         super().__init__(sampling_strategy=sampling_strategy)
         self.random_state = random_state
 
diff --git a/imblearn/over_sampling/_smote.py b/imblearn/over_sampling/_smote.py
index a141d4b04..f5ce02ad2 100644
--- a/imblearn/over_sampling/_smote.py
+++ b/imblearn/over_sampling/_smote.py
@@ -30,6 +30,7 @@
 from ..utils import Substitution
 from ..utils._docstring import _n_jobs_docstring
 from ..utils._docstring import _random_state_docstring
+from ..utils._validation import _deprecate_positional_args
 
 
 class BaseSMOTE(BaseOverSampler):
@@ -297,8 +298,10 @@ class BorderlineSMOTE(BaseSMOTE):
     Resampled dataset shape Counter({{0: 900, 1: 900}})
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         sampling_strategy="auto",
         random_state=None,
         k_neighbors=5,
@@ -495,8 +498,10 @@ class SVMSMOTE(BaseSMOTE):
     Resampled dataset shape Counter({{0: 900, 1: 900}})
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         sampling_strategy="auto",
         random_state=None,
         k_neighbors=5,
@@ -696,8 +701,10 @@ class SMOTE(BaseSMOTE):
     Resampled dataset shape Counter({{0: 900, 1: 900}})
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         sampling_strategy="auto",
         random_state=None,
         k_neighbors=5,
@@ -873,9 +880,11 @@ class SMOTENC(SMOTE):
 
     _required_parameters = ["categorical_features"]
 
+    @_deprecate_positional_args
     def __init__(
         self,
         categorical_features,
+        *,
         sampling_strategy="auto",
         random_state=None,
         k_neighbors=5,
@@ -1142,8 +1151,10 @@ class KMeansSMOTE(BaseSMOTE):
     More 0 samples: True
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         sampling_strategy="auto",
         random_state=None,
         k_neighbors=2,
diff --git a/imblearn/tensorflow/_generator.py b/imblearn/tensorflow/_generator.py
index 6c5b32872..669904351 100644
--- a/imblearn/tensorflow/_generator.py
+++ b/imblearn/tensorflow/_generator.py
@@ -9,12 +9,15 @@
 from ..under_sampling import RandomUnderSampler
 from ..utils import Substitution
 from ..utils._docstring import _random_state_docstring
+from ..utils._validation import _deprecate_positional_args
 
 
 @Substitution(random_state=_random_state_docstring)
+@_deprecate_positional_args
 def balanced_batch_generator(
     X,
     y,
+    *,
     sample_weight=None,
     sampler=None,
     batch_size=32,
diff --git a/imblearn/under_sampling/_prototype_generation/_cluster_centroids.py b/imblearn/under_sampling/_prototype_generation/_cluster_centroids.py
index 333b1d7cc..ebdbed27b 100644
--- a/imblearn/under_sampling/_prototype_generation/_cluster_centroids.py
+++ b/imblearn/under_sampling/_prototype_generation/_cluster_centroids.py
@@ -20,6 +20,7 @@
 from ...utils import Substitution
 from ...utils._docstring import _n_jobs_docstring
 from ...utils._docstring import _random_state_docstring
+from ...utils._validation import _deprecate_positional_args
 
 VOTING_KIND = ("auto", "hard", "soft")
 
@@ -96,8 +97,10 @@ class ClusterCentroids(BaseUnderSampler):
     Resampled dataset shape Counter({{...}})
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         sampling_strategy="auto",
         random_state=None,
         estimator=None,
diff --git a/imblearn/under_sampling/_prototype_selection/_condensed_nearest_neighbour.py b/imblearn/under_sampling/_prototype_selection/_condensed_nearest_neighbour.py
index 8d79f5758..a3bf1e50e 100644
--- a/imblearn/under_sampling/_prototype_selection/_condensed_nearest_neighbour.py
+++ b/imblearn/under_sampling/_prototype_selection/_condensed_nearest_neighbour.py
@@ -19,6 +19,7 @@
 from ...utils import Substitution
 from ...utils._docstring import _n_jobs_docstring
 from ...utils._docstring import _random_state_docstring
+from ...utils._validation import _deprecate_positional_args
 
 
 @Substitution(
@@ -94,8 +95,10 @@ class CondensedNearestNeighbour(BaseCleaningSampler):
     Resampled dataset shape Counter({{-1: 268, 1: 227}}) # doctest: +SKIP
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         sampling_strategy="auto",
         random_state=None,
         n_neighbors=None,
diff --git a/imblearn/under_sampling/_prototype_selection/_edited_nearest_neighbours.py b/imblearn/under_sampling/_prototype_selection/_edited_nearest_neighbours.py
index 41d62c622..6d2de1f3d 100644
--- a/imblearn/under_sampling/_prototype_selection/_edited_nearest_neighbours.py
+++ b/imblearn/under_sampling/_prototype_selection/_edited_nearest_neighbours.py
@@ -17,6 +17,7 @@
 from ...utils import check_neighbors_object
 from ...utils import Substitution
 from ...utils._docstring import _n_jobs_docstring
+from ...utils._validation import _deprecate_positional_args
 
 SEL_KIND = ("all", "mode")
 
@@ -99,8 +100,9 @@ class EditedNearestNeighbours(BaseCleaningSampler):
     Resampled dataset shape Counter({{1: 887, 0: 100}})
     """
 
+    @_deprecate_positional_args
     def __init__(
-        self, sampling_strategy="auto", n_neighbors=3, kind_sel="all",
+        self, *, sampling_strategy="auto", n_neighbors=3, kind_sel="all",
         n_jobs=None
     ):
         super().__init__(sampling_strategy=sampling_strategy)
@@ -246,8 +248,10 @@ class RepeatedEditedNearestNeighbours(BaseCleaningSampler):
     Resampled dataset shape Counter({{1: 887, 0: 100}})
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         sampling_strategy="auto",
         n_neighbors=3,
         max_iter=100,
@@ -423,8 +427,10 @@ class without early stopping.
     Resampled dataset shape Counter({{1: 887, 0: 100}})
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         sampling_strategy="auto",
         n_neighbors=3,
         kind_sel="all",
diff --git a/imblearn/under_sampling/_prototype_selection/_instance_hardness_threshold.py b/imblearn/under_sampling/_prototype_selection/_instance_hardness_threshold.py
index 9edd2ab11..f1e4ae9ec 100644
--- a/imblearn/under_sampling/_prototype_selection/_instance_hardness_threshold.py
+++ b/imblearn/under_sampling/_prototype_selection/_instance_hardness_threshold.py
@@ -22,6 +22,7 @@
 from ...utils import Substitution
 from ...utils._docstring import _n_jobs_docstring
 from ...utils._docstring import _random_state_docstring
+from ...utils._validation import _deprecate_positional_args
 
 
 @Substitution(
@@ -97,8 +98,10 @@ class InstanceHardnessThreshold(BaseUnderSampler):
     Resampled dataset shape Counter({{1: 5..., 0: 100}})
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         estimator=None,
         sampling_strategy="auto",
         random_state=None,
diff --git a/imblearn/under_sampling/_prototype_selection/_nearmiss.py b/imblearn/under_sampling/_prototype_selection/_nearmiss.py
index 0dd567a68..bf426ff3a 100644
--- a/imblearn/under_sampling/_prototype_selection/_nearmiss.py
+++ b/imblearn/under_sampling/_prototype_selection/_nearmiss.py
@@ -15,6 +15,7 @@
 from ...utils import check_neighbors_object
 from ...utils import Substitution
 from ...utils._docstring import _n_jobs_docstring
+from ...utils._validation import _deprecate_positional_args
 
 
 @Substitution(
@@ -93,8 +94,10 @@ class NearMiss(BaseUnderSampler):
     Resampled dataset shape Counter({{0: 100, 1: 100}})
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         sampling_strategy="auto",
         version=1,
         n_neighbors=3,
diff --git a/imblearn/under_sampling/_prototype_selection/_neighbourhood_cleaning_rule.py b/imblearn/under_sampling/_prototype_selection/_neighbourhood_cleaning_rule.py
index 6222da83b..01381453d 100644
--- a/imblearn/under_sampling/_prototype_selection/_neighbourhood_cleaning_rule.py
+++ b/imblearn/under_sampling/_prototype_selection/_neighbourhood_cleaning_rule.py
@@ -16,6 +16,7 @@
 from ...utils import check_neighbors_object
 from ...utils import Substitution
 from ...utils._docstring import _n_jobs_docstring
+from ...utils._validation import _deprecate_positional_args
 
 SEL_KIND = ("all", "mode")
 
@@ -101,8 +102,10 @@ class NeighbourhoodCleaningRule(BaseCleaningSampler):
     Resampled dataset shape Counter({{1: 877, 0: 100}})
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         sampling_strategy="auto",
         n_neighbors=3,
         kind_sel="all",
diff --git a/imblearn/under_sampling/_prototype_selection/_one_sided_selection.py b/imblearn/under_sampling/_prototype_selection/_one_sided_selection.py
index 81cf1799e..93c753e97 100644
--- a/imblearn/under_sampling/_prototype_selection/_one_sided_selection.py
+++ b/imblearn/under_sampling/_prototype_selection/_one_sided_selection.py
@@ -17,6 +17,7 @@
 from ...utils import Substitution
 from ...utils._docstring import _n_jobs_docstring
 from ...utils._docstring import _random_state_docstring
+from ...utils._validation import _deprecate_positional_args
 
 
 @Substitution(
@@ -88,8 +89,10 @@ class OneSidedSelection(BaseCleaningSampler):
     Resampled dataset shape Counter({{1: 496, 0: 100}})
     """
 
+    @_deprecate_positional_args
     def __init__(
         self,
+        *,
         sampling_strategy="auto",
         random_state=None,
         n_neighbors=None,
diff --git a/imblearn/under_sampling/_prototype_selection/_random_under_sampler.py b/imblearn/under_sampling/_prototype_selection/_random_under_sampler.py
index 805e0907e..b5ec14dae 100644
--- a/imblearn/under_sampling/_prototype_selection/_random_under_sampler.py
+++ b/imblearn/under_sampling/_prototype_selection/_random_under_sampler.py
@@ -13,6 +13,7 @@
 from ...utils import check_target_type
 from ...utils import Substitution
 from ...utils._docstring import _random_state_docstring
+from ...utils._validation import _deprecate_positional_args
 
 
 @Substitution(
@@ -71,8 +72,9 @@ class RandomUnderSampler(BaseUnderSampler):
     Resampled dataset shape Counter({{0: 100, 1: 100}})
     """
 
+    @_deprecate_positional_args
     def __init__(
-        self, sampling_strategy="auto", random_state=None, replacement=False
+        self, *, sampling_strategy="auto", random_state=None, replacement=False
     ):
         super().__init__(sampling_strategy=sampling_strategy)
         self.random_state = random_state
diff --git a/imblearn/under_sampling/_prototype_selection/_tomek_links.py b/imblearn/under_sampling/_prototype_selection/_tomek_links.py
index 4bf9d880a..1105bbbc6 100644
--- a/imblearn/under_sampling/_prototype_selection/_tomek_links.py
+++ b/imblearn/under_sampling/_prototype_selection/_tomek_links.py
@@ -12,6 +12,7 @@
 from ..base import BaseCleaningSampler
 from ...utils import Substitution
 from ...utils._docstring import _n_jobs_docstring
+from ...utils._validation import _deprecate_positional_args
 
 
 @Substitution(
@@ -74,7 +75,8 @@ class TomekLinks(BaseCleaningSampler):
     Resampled dataset shape Counter({{1: 897, 0: 100}})
     """
 
-    def __init__(self, sampling_strategy="auto", n_jobs=None):
+    @_deprecate_positional_args
+    def __init__(self, *, sampling_strategy="auto", n_jobs=None):
         super().__init__(sampling_strategy=sampling_strategy)
         self.n_jobs = n_jobs
 
diff --git a/imblearn/under_sampling/_prototype_selection/tests/test_instance_hardness_threshold.py b/imblearn/under_sampling/_prototype_selection/tests/test_instance_hardness_threshold.py
index 967f2d468..18db03a99 100644
--- a/imblearn/under_sampling/_prototype_selection/tests/test_instance_hardness_threshold.py
+++ b/imblearn/under_sampling/_prototype_selection/tests/test_instance_hardness_threshold.py
@@ -41,7 +41,8 @@
 def test_iht_init():
     sampling_strategy = "auto"
     iht = InstanceHardnessThreshold(
-        ESTIMATOR, sampling_strategy=sampling_strategy, random_state=RND_SEED
+        estimator=ESTIMATOR, sampling_strategy=sampling_strategy,
+        random_state=RND_SEED,
     )
 
     assert iht.sampling_strategy == sampling_strategy
@@ -49,7 +50,9 @@ def test_iht_init():
 
 
 def test_iht_fit_resample():
-    iht = InstanceHardnessThreshold(ESTIMATOR, random_state=RND_SEED)
+    iht = InstanceHardnessThreshold(
+        estimator=ESTIMATOR, random_state=RND_SEED
+    )
     X_resampled, y_resampled = iht.fit_resample(X, Y)
     assert X_resampled.shape == (12, 2)
     assert y_resampled.shape == (12,)
@@ -58,7 +61,8 @@ def test_iht_fit_resample():
 def test_iht_fit_resample_half():
     sampling_strategy = {0: 3, 1: 3}
     iht = InstanceHardnessThreshold(
-        NB(), sampling_strategy=sampling_strategy, random_state=RND_SEED
+        estimator=NB(), sampling_strategy=sampling_strategy,
+        random_state=RND_SEED
     )
     X_resampled, y_resampled = iht.fit_resample(X, Y)
     assert X_resampled.shape == (6, 2)
diff --git a/imblearn/utils/_validation.py b/imblearn/utils/_validation.py
index 1ebbedcd2..a46918b0c 100644
--- a/imblearn/utils/_validation.py
+++ b/imblearn/utils/_validation.py
@@ -5,6 +5,8 @@
 
 import warnings
 from collections import OrderedDict
+from functools import wraps
+from inspect import signature, Parameter
 from numbers import Integral, Real
 
 import numpy as np
@@ -599,3 +601,41 @@ def check_sampling_strategy(sampling_strategy, y, sampling_type, **kwargs):
     "all": _sampling_strategy_all,
     "auto": _sampling_strategy_auto,
 }
+
+
+def _deprecate_positional_args(f):
+    """Decorator for methods that issues warnings for positional arguments
+
+    Using the keyword-only argument syntax in pep 3102, arguments after the
+    * will issue a warning when passed as a positional argument.
+
+    Parameters
+    ----------
+    f : function
+        function to check arguments on
+    """
+    sig = signature(f)
+    kwonly_args = []
+    all_args = []
+
+    for name, param in sig.parameters.items():
+        if param.kind == Parameter.POSITIONAL_OR_KEYWORD:
+            all_args.append(name)
+        elif param.kind == Parameter.KEYWORD_ONLY:
+            kwonly_args.append(name)
+
+    @wraps(f)
+    def inner_f(*args, **kwargs):
+        extra_args = len(args) - len(all_args)
+        if extra_args > 0:
+            # ignore first 'self' argument for instance methods
+            args_msg = ['{}={}'.format(name, arg)
+                        for name, arg in zip(kwonly_args[:extra_args],
+                                             args[-extra_args:])]
+            warnings.warn("Pass {} as keyword args. From version 0.9 "
+                          "passing these as positional arguments will "
+                          "result in an error".format(", ".join(args_msg)),
+                          FutureWarning)
+        kwargs.update({k: arg for k, arg in zip(sig.parameters, args)})
+        return f(**kwargs)
+    return inner_f
diff --git a/imblearn/utils/tests/test_validation.py b/imblearn/utils/tests/test_validation.py
index 0f4dcb98b..e4f9c01c8 100644
--- a/imblearn/utils/tests/test_validation.py
+++ b/imblearn/utils/tests/test_validation.py
@@ -18,6 +18,7 @@
 from imblearn.utils import check_sampling_strategy
 from imblearn.utils import check_target_type
 from imblearn.utils._validation import ArraysTransformer
+from imblearn.utils._validation import _deprecate_positional_args
 
 multiclass_target = np.array([1] * 50 + [2] * 100 + [3] * 25)
 binary_target = np.array([1] * 25 + [0] * 100)
@@ -366,3 +367,35 @@ def test_arrays_transformer_pandas():
     assert isinstance(y_res, pd.Series)
     assert_array_equal(y_res.name, y_s.name)
     assert_array_equal(y_res.dtype, y_s.dtype)
+
+
+def test_deprecate_positional_args_warns_for_function():
+
+    @_deprecate_positional_args
+    def f1(a, b, *, c=1, d=1):
+        pass
+
+    with pytest.warns(FutureWarning,
+                      match=r"Pass c=3 as keyword args"):
+        f1(1, 2, 3)
+
+    with pytest.warns(FutureWarning,
+                      match=r"Pass c=3, d=4 as keyword args"):
+        f1(1, 2, 3, 4)
+
+    @_deprecate_positional_args
+    def f2(a=1, *, b=1, c=1, d=1):
+        pass
+
+    with pytest.warns(FutureWarning,
+                      match=r"Pass b=2 as keyword args"):
+        f2(1, 2)
+
+    # The * is place before a keyword only argument without a default value
+    @_deprecate_positional_args
+    def f3(a, *, b, c=1, d=1):
+        pass
+
+    with pytest.warns(FutureWarning,
+                      match=r"Pass b=2 as keyword args"):
+        f3(1, 2)