diff --git a/doc/source/whatsnew/v1.2.1.rst b/doc/source/whatsnew/v1.2.1.rst
index a1612117072a5..b1f8389420cd9 100644
--- a/doc/source/whatsnew/v1.2.1.rst
+++ b/doc/source/whatsnew/v1.2.1.rst
@@ -10,6 +10,20 @@ including other versions of pandas.
 
 .. ---------------------------------------------------------------------------
 
+.. _whatsnew_121.api_breaking:
+
+Backwards incompatible API changes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. _whatsnew_121.api_breaking.testing.assert_frame_equal:
+
+Added ``check_freq`` argument to ``testing.assert_frame_equal``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ``check_freq`` argument was added to :func:`testing.assert_frame_equal` in pandas 1.1.0 and defaults to ``True``. :func:`testing.assert_frame_equal` now raises ``AssertionError`` if the indexes do not have the same frequency. Before pandas 1.1.0, the index frequency was not checked by :func:`testing.assert_frame_equal`.
+
+.. ---------------------------------------------------------------------------
+
 .. _whatsnew_121.regressions:
 
 Fixed regressions
diff --git a/pandas/_testing/asserters.py b/pandas/_testing/asserters.py
index ba4410bd95940..13115d6b959d9 100644
--- a/pandas/_testing/asserters.py
+++ b/pandas/_testing/asserters.py
@@ -1128,6 +1128,8 @@ def assert_frame_equal(
         (same as in columns) - same labels must be with the same data.
     check_freq : bool, default True
         Whether to check the `freq` attribute on a DatetimeIndex or TimedeltaIndex.
+
+        .. versionadded:: 1.1.0
     check_flags : bool, default True
         Whether to check the `flags` attribute.
     rtol : float, default 1e-5