diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index d116714..a2f610b 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -1,6 +1,11 @@
 Releases
 ========
 
+UNRELEASED
+----------
+
+* `#646 <https://github.com/pytest-dev/pytest-mock/pull/646>`_: ``mocker.resetall(side_effect=True)`` no longer removes the warning about using mocks returned by ``mocker.patch`` and friends as context managers.
+
 3.17.0
 ------
 
diff --git a/src/pytest_mock/plugin.py b/src/pytest_mock/plugin.py
index 71e5c2b..f448e51 100644
--- a/src/pytest_mock/plugin.py
+++ b/src/pytest_mock/plugin.py
@@ -56,6 +56,10 @@ class MockCacheItem:
     is_spy: bool = False
     # The ``side_effect`` a spy uses to call the spied code, restored by ``resetall``.
     spy_side_effect: Callable[..., Any] | None = None
+    # ``mock.__enter__`` and its ``side_effect`` that warns about using the mock
+    # as a context manager, restored by ``resetall``.
+    enter_mock: Any | None = None
+    enter_side_effect: Callable[[], None] | None = None
     # The objects ``resetall`` resets instead of ``mock``, for patches such as
     # ``patch.multiple`` whose ``mock`` is a dict of the patched values.
     reset_mocks: tuple[Any, ...] | None = None
@@ -168,6 +172,10 @@ def resetall(
             # it means going back to that, not to ``None``.
             if side_effect and mock_item.spy_side_effect is not None:
                 mock_item.mock.side_effect = mock_item.spy_side_effect
+            # Resetting ``side_effect`` also clears it on ``__enter__``, which
+            # would drop the warning about using the mock as a context manager.
+            if side_effect and mock_item.enter_mock is not None:
+                mock_item.enter_mock.side_effect = mock_item.enter_side_effect
 
     def _reset_mock(self, mock: Any, *, return_value: bool, side_effect: bool) -> None:
         # See issue #237.
@@ -307,7 +315,7 @@ def _start_patch(
             """
             p = mock_func(*args, **kwargs)
             mocked: MockType = p.start()
-            self.__mock_cache.add(mock=mocked, patch=p)
+            mock_item = self.__mock_cache.add(mock=mocked, patch=p)
             if hasattr(mocked, "reset_mock"):  # noqa:SIM102
                 # check if `mocked` is actually a mock object, as depending on autospec or target
                 # parameters `mocked` can be anything
@@ -320,6 +328,8 @@ def _start_patch(
                         PytestMockWarning,
                         stacklevel=5,
                     )
+                    mock_item.enter_mock = mocked.__enter__
+                    mock_item.enter_side_effect = mocked.__enter__.side_effect
             return mocked
 
         def object(
diff --git a/tests/test_pytest_mock.py b/tests/test_pytest_mock.py
index 8921e6d..e74ca8d 100644
--- a/tests/test_pytest_mock.py
+++ b/tests/test_pytest_mock.py
@@ -1818,6 +1818,52 @@ def test_patch(self, mocker: MockerFixture) -> None:
 
         assert warn_record[0].filename == __file__
 
+    def test_patch_after_resetall(self, mocker: MockerFixture) -> None:
+        """``resetall(side_effect=True)`` keeps the warning (#637)."""
+        mocked = mocker.patch("json.loads")
+        mocker.resetall(return_value=True, side_effect=True)
+
+        with pytest.warns(PytestMockWarning) as warn_record, mocked:
+            pass
+
+        assert warn_record[0].filename == __file__
+
+    def test_patch_deleted_enter_after_resetall(self, mocker: MockerFixture) -> None:
+        """``resetall(side_effect=True)`` leaves a deleted ``__enter__`` alone."""
+        mocked = mocker.patch("json.loads")
+        del mocked.__enter__
+        mocker.resetall(side_effect=True)
+
+        assert not hasattr(mocked, "__enter__")
+
+    def test_spy_after_resetall(self, mocker: MockerFixture) -> None:
+        """Spies backed by a ``MagicMock`` also keep the warning after
+        ``resetall(side_effect=True)`` (#637)."""
+        expected = os.getcwd()
+        spy = mocker.spy(os, "getcwd")
+        mocker.resetall(side_effect=True)
+
+        with pytest.warns(PytestMockWarning), spy:
+            pass
+        assert os.getcwd() == expected
+
+    def test_patch_context_manager_after_resetall(self, mocker: MockerFixture) -> None:
+        """``resetall`` does not add the warning to ``patch.context_manager``."""
+
+        class A:
+            def doIt(self):
+                return False
+
+        a = A()
+        mocked = mocker.patch.context_manager(a, "doIt", return_value=True)
+        mocker.resetall(side_effect=True)
+
+        with warnings.catch_warnings(record=True) as warn_record:  # noqa:SIM117
+            with mocked:
+                pass
+
+        assert len(warn_record) == 0
+
     def test_patching_a_context_manager(self, mocker: MockerFixture) -> None:
         """Our message about misusing mocker as a context manager should not affect mocking
         context managers (see #192)"""