diff --git a/changelog/6267.feature.rst b/changelog/6267.feature.rst
new file mode 100644
index 00000000000..268ebc24130
--- /dev/null
+++ b/changelog/6267.feature.rst
@@ -0,0 +1,2 @@
+When output is close to truncation limit, we now write 'N lines hidden [1 truncated]',
+instead of 'N+1 lines hidden' - last line which we show isn't really hidden always, neither it's always really truncated.
diff --git a/src/_pytest/assertion/truncate.py b/src/_pytest/assertion/truncate.py
index d97b05b441e..dc8fd3c4c2e 100644
--- a/src/_pytest/assertion/truncate.py
+++ b/src/_pytest/assertion/truncate.py
@@ -40,6 +40,8 @@ def _truncate_explanation(input_lines, max_lines=None, max_chars=None):
 
     Truncates to either 8 lines, or 640 characters - whichever the input reaches
     first. The remaining lines will be replaced by a usage message.
+
+    Check https://github.com/pytest-dev/pytest/issues/6267 for corner cases
     """
 
     if max_lines is None:
@@ -62,12 +64,18 @@ def _truncate_explanation(input_lines, max_lines=None, max_chars=None):
 
     # Append useful message to explanation
     truncated_line_count = len(input_lines) - len(truncated_explanation)
-    truncated_line_count += 1  # Account for the part-truncated final line
     msg = "...Full output truncated"
+    last_truncated = not (
+        input_lines[len(truncated_explanation) - 1] in truncated_explanation[-1]
+    )
     if truncated_line_count == 1:
-        msg += " ({} line hidden)".format(truncated_line_count)
+        msg += " ({} line hidden".format(truncated_line_count)
+    else:
+        msg += " ({} lines hidden".format(truncated_line_count)
+    if last_truncated:
+        msg += ", 1 truncated)"
     else:
-        msg += " ({} lines hidden)".format(truncated_line_count)
+        msg += ")"
     msg += ", {}".format(USAGE_MSG)
     truncated_explanation.extend(["", str(msg)])
     return truncated_explanation