diff --git a/Tests/helper.py b/Tests/helper.py
index 5d206f6449a..8510a05f067 100644
--- a/Tests/helper.py
+++ b/Tests/helper.py
@@ -300,7 +300,12 @@ def _cached_hopper(mode: str) -> Image.Image:
         im = hopper("L")
     else:
         im = hopper()
-    return im.convert(mode)
+    if mode.startswith("BGR;"):
+        with pytest.warns(DeprecationWarning):
+            im = im.convert(mode)
+    else:
+        im = im.convert(mode)
+    return im
 
 
 def djpeg_available() -> bool:
diff --git a/Tests/test_image.py b/Tests/test_image.py
index 8e7e40c05da..b7f81408000 100644
--- a/Tests/test_image.py
+++ b/Tests/test_image.py
@@ -36,10 +36,19 @@
 )
 
 
+# Deprecation helper
+def helper_image_new(mode: str, size: tuple[int, int]) -> Image.Image:
+    if mode.startswith("BGR;"):
+        with pytest.warns(DeprecationWarning):
+            return Image.new(mode, size)
+    else:
+        return Image.new(mode, size)
+
+
 class TestImage:
     @pytest.mark.parametrize("mode", modes)
     def test_image_modes_success(self, mode: str) -> None:
-        Image.new(mode, (1, 1))
+        helper_image_new(mode, (1, 1))
 
     @pytest.mark.parametrize("mode", ("", "bad", "very very long"))
     def test_image_modes_fail(self, mode: str) -> None:
@@ -1023,7 +1032,11 @@ def test_roundtrip_bytes_constructor(self, mode: str) -> None:
         im = hopper(mode)
         source_bytes = im.tobytes()
 
-        reloaded = Image.frombytes(mode, im.size, source_bytes)
+        if mode.startswith("BGR;"):
+            with pytest.warns(DeprecationWarning):
+                reloaded = Image.frombytes(mode, im.size, source_bytes)
+        else:
+            reloaded = Image.frombytes(mode, im.size, source_bytes)
         assert reloaded.tobytes() == source_bytes
 
     @pytest.mark.parametrize("mode", modes)
@@ -1031,7 +1044,7 @@ def test_roundtrip_bytes_method(self, mode: str) -> None:
         im = hopper(mode)
         source_bytes = im.tobytes()
 
-        reloaded = Image.new(mode, im.size)
+        reloaded = helper_image_new(mode, im.size)
         reloaded.frombytes(source_bytes)
         assert reloaded.tobytes() == source_bytes
 
@@ -1040,7 +1053,7 @@ def test_getdata_putdata(self, mode: str) -> None:
         if is_big_endian and mode == "BGR;15":
             pytest.xfail("Known failure of BGR;15 on big-endian")
         im = hopper(mode)
-        reloaded = Image.new(mode, im.size)
+        reloaded = helper_image_new(mode, im.size)
         reloaded.putdata(im.getdata())
         assert_image_equal(im, reloaded)
 
diff --git a/Tests/test_image_access.py b/Tests/test_image_access.py
index 2cd2e0c34e5..02c75073add 100644
--- a/Tests/test_image_access.py
+++ b/Tests/test_image_access.py
@@ -207,7 +207,11 @@ def check(self, mode: str, expected_color_int: int | None = None) -> None:
 
     @pytest.mark.parametrize("mode", modes)
     def test_basic(self, mode: str) -> None:
-        self.check(mode)
+        if mode.startswith("BGR;"):
+            with pytest.warns(DeprecationWarning):
+                self.check(mode)
+        else:
+            self.check(mode)
 
     def test_list(self) -> None:
         im = hopper()
diff --git a/Tests/test_image_putdata.py b/Tests/test_image_putdata.py
index 73145faac15..dad26ef144c 100644
--- a/Tests/test_image_putdata.py
+++ b/Tests/test_image_putdata.py
@@ -81,7 +81,8 @@ def test_mode_F() -> None:
 @pytest.mark.parametrize("mode", ("BGR;15", "BGR;16", "BGR;24"))
 def test_mode_BGR(mode: str) -> None:
     data = [(16, 32, 49), (32, 32, 98)]
-    im = Image.new(mode, (1, 2))
+    with pytest.warns(DeprecationWarning):
+        im = Image.new(mode, (1, 2))
     im.putdata(data)
 
     assert list(im.getdata()) == data
diff --git a/Tests/test_lib_pack.py b/Tests/test_lib_pack.py
index f34ff7d0230..b4a300d0c59 100644
--- a/Tests/test_lib_pack.py
+++ b/Tests/test_lib_pack.py
@@ -362,11 +362,14 @@ def test_RGB(self) -> None:
         )
 
     def test_BGR(self) -> None:
-        self.assert_unpack("BGR;15", "BGR;15", 3, (8, 131, 0), (24, 0, 8), (41, 131, 8))
-        self.assert_unpack(
-            "BGR;16", "BGR;16", 3, (8, 64, 0), (24, 129, 0), (41, 194, 0)
-        )
-        self.assert_unpack("BGR;24", "BGR;24", 3, (1, 2, 3), (4, 5, 6), (7, 8, 9))
+        with pytest.warns(DeprecationWarning):
+            self.assert_unpack(
+                "BGR;15", "BGR;15", 3, (8, 131, 0), (24, 0, 8), (41, 131, 8)
+            )
+            self.assert_unpack(
+                "BGR;16", "BGR;16", 3, (8, 64, 0), (24, 129, 0), (41, 194, 0)
+            )
+            self.assert_unpack("BGR;24", "BGR;24", 3, (1, 2, 3), (4, 5, 6), (7, 8, 9))
 
     def test_RGBA(self) -> None:
         self.assert_unpack("RGBA", "LA", 2, (1, 1, 1, 2), (3, 3, 3, 4), (5, 5, 5, 6))
diff --git a/docs/deprecations.rst b/docs/deprecations.rst
index 7882ec5ee2b..b2cd968fee3 100644
--- a/docs/deprecations.rst
+++ b/docs/deprecations.rst
@@ -100,6 +100,13 @@ ImageMath eval()
 ``ImageMath.eval()`` has been deprecated. Use :py:meth:`~PIL.ImageMath.lambda_eval` or
 :py:meth:`~PIL.ImageMath.unsafe_eval` instead.
 
+BGR;15, BGR 16 and BGR;24
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. deprecated:: 10.4.0
+
+The experimental BGR;15, BGR;16 and BGR;24 modes have been deprecated.
+
 Support for LibTIFF earlier than 4
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
diff --git a/docs/handbook/concepts.rst b/docs/handbook/concepts.rst
index e0975a12132..5094dbf3f27 100644
--- a/docs/handbook/concepts.rst
+++ b/docs/handbook/concepts.rst
@@ -59,9 +59,6 @@ Pillow also provides limited support for a few additional modes, including:
     * ``I;16L`` (16-bit little endian unsigned integer pixels)
     * ``I;16B`` (16-bit big endian unsigned integer pixels)
     * ``I;16N`` (16-bit native endian unsigned integer pixels)
-    * ``BGR;15`` (15-bit reversed true colour)
-    * ``BGR;16`` (16-bit reversed true colour)
-    * ``BGR;24`` (24-bit reversed true colour)
 
 Premultiplied alpha is where the values for each other channel have been
 multiplied by the alpha. For example, an RGBA pixel of ``(10, 20, 30, 127)``
diff --git a/docs/releasenotes/10.4.0.rst b/docs/releasenotes/10.4.0.rst
index 0c2926732e4..3150bf4e02f 100644
--- a/docs/releasenotes/10.4.0.rst
+++ b/docs/releasenotes/10.4.0.rst
@@ -23,6 +23,11 @@ TODO
 Deprecations
 ============
 
+BGR;15, BGR 16 and BGR;24
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The experimental BGR;15, BGR;16 and BGR;24 modes have been deprecated.
+
 Support for LibTIFF earlier than 4
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index c65cf38500a..a17edfa391c 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -55,6 +55,7 @@
     _plugins,
 )
 from ._binary import i32le, o32be, o32le
+from ._deprecate import deprecate
 from ._typing import StrOrBytesPath, TypeGuard
 from ._util import DeferredError, is_path
 
@@ -939,6 +940,9 @@ def convert(
         :returns: An :py:class:`~PIL.Image.Image` object.
         """
 
+        if mode in ("BGR;15", "BGR;16", "BGR;24"):
+            deprecate(mode, 12)
+
         self.load()
 
         has_transparency = "transparency" in self.info
@@ -2956,6 +2960,9 @@ def new(
     :returns: An :py:class:`~PIL.Image.Image` object.
     """
 
+    if mode in ("BGR;15", "BGR;16", "BGR;24"):
+        deprecate(mode, 12)
+
     _check_size(size)
 
     if color is None:
diff --git a/src/PIL/ImageMode.py b/src/PIL/ImageMode.py
index 5e05c5f43ed..7bd2afcf2fa 100644
--- a/src/PIL/ImageMode.py
+++ b/src/PIL/ImageMode.py
@@ -18,6 +18,8 @@
 from functools import lru_cache
 from typing import NamedTuple
 
+from ._deprecate import deprecate
+
 
 class ModeDescriptor(NamedTuple):
     """Wrapper for mode strings."""
@@ -63,6 +65,8 @@ def getmode(mode: str) -> ModeDescriptor:
         "PA": ("RGB", "L", ("P", "A"), "|u1"),
     }
     if mode in modes:
+        if mode in ("BGR;15", "BGR;16", "BGR;24"):
+            deprecate(mode, 12)
         base_mode, base_type, bands, type_str = modes[mode]
         return ModeDescriptor(mode, bands, base_mode, base_type, type_str)