diff --git a/sql/core/src/main/scala/org/apache/spark/sql/RelationalGroupedDataset.scala b/sql/core/src/main/scala/org/apache/spark/sql/RelationalGroupedDataset.scala
index 53d732403f979..25d71aa825018 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/RelationalGroupedDataset.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/RelationalGroupedDataset.scala
@@ -388,6 +388,16 @@ class RelationalGroupedDataset protected[sql](
     pivot(pivotColumn, values.asScala)
   }
 
+  /**
+   * Returns all grouping column names as an array.
+   *
+   * @since 2.1.0
+   */
+  def columns: Array[String] = {
+    val groupingNamedExpressions = groupingExprs.map(alias)
+    groupingNamedExpressions.map(_.name).toArray
+  }
+
   /**
    * Applies the given serialized R function `func` to each group of data. For each unique group,
    * the function will be passed the group key and an iterator that contains all of the elements in
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/DataFrameAggregateSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/DataFrameAggregateSuite.scala
index 69a3b5f278fd8..043822363c35a 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/DataFrameAggregateSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/DataFrameAggregateSuite.scala
@@ -85,6 +85,9 @@ class DataFrameAggregateSuite extends QueryTest with SharedSQLContext {
         Row(new java.math.BigDecimal(3.0), new java.math.BigDecimal(3.0)),
         Row(null, new java.math.BigDecimal(2.0)))
     )
+
+    assert(df1.groupBy("key").columns.sameElements(Array("key")))
+    assert(df1.groupBy("value1", "value2").columns.sameElements(Array("value1", "value2")))
   }
 
   test("SPARK-17124 agg should be ordering preserving") {