diff --git a/Tests/test_image.py b/Tests/test_image.py
index 1aa810e22..83b027aa2 100644
--- a/Tests/test_image.py
+++ b/Tests/test_image.py
@@ -1132,10 +1132,6 @@ class TestImage:
             assert len(caplog.records) == 0
             assert im.fp is None
 
-    def test_deprecation(self) -> None:
-        with pytest.warns(DeprecationWarning, match="Image.isImageType"):
-            assert not Image.isImageType(None)
-
 
 class TestImageBytes:
     @pytest.mark.parametrize("mode", Image.MODES)
diff --git a/docs/deprecations.rst b/docs/deprecations.rst
index b4eb1fa4c..5ecd7de42 100644
--- a/docs/deprecations.rst
+++ b/docs/deprecations.rst
@@ -123,14 +123,6 @@ ICNS (width, height, scale) sizes
 Setting an ICNS image size to ``(width, height, scale)`` before loading has been
 deprecated. Instead, ``load(scale)`` can be used.
 
-Image isImageType()
-^^^^^^^^^^^^^^^^^^^
-
-.. deprecated:: 11.0.0
-
-``Image.isImageType(im)`` has been deprecated. Use ``isinstance(im, Image.Image)``
-instead.
-
 ImageMath.lambda_eval and ImageMath.unsafe_eval options parameter
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
@@ -222,6 +214,15 @@ BGR;15, BGR 16 and BGR;24
 
 The experimental BGR;15, BGR;16 and BGR;24 modes have been removed.
 
+Image isImageType()
+^^^^^^^^^^^^^^^^^^^
+
+.. deprecated:: 11.0.0
+.. versionremoved:: 12.0.0
+
+``Image.isImageType(im)`` has been removed. Use ``isinstance(im, Image.Image)``
+instead.
+
 TiffImagePlugin IFD_LEGACY_API
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index 9df253498..59168f5e3 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -115,21 +115,6 @@ except ImportError as v:
     raise
 
 
-def isImageType(t: Any) -> TypeGuard[Image]:
-    """
-    Checks if an object is an image object.
-
-    .. warning::
-
-       This function is for internal use only.
-
-    :param t: object to check if it's an image
-    :returns: True if the object is an image
-    """
-    deprecate("Image.isImageType(im)", 12, "isinstance(im, Image.Image)")
-    return hasattr(t, "im")
-
-
 #
 # Constants
 
@@ -219,7 +204,7 @@ if TYPE_CHECKING:
     from IPython.lib.pretty import PrettyPrinter
 
     from . import ImageFile, ImageFilter, ImagePalette, ImageQt, TiffImagePlugin
-    from ._typing import CapsuleType, NumpyArray, StrOrBytesPath, TypeGuard
+    from ._typing import CapsuleType, NumpyArray, StrOrBytesPath
 ID: list[str] = []
 OPEN: dict[
     str,