diff --git a/tests/test_cli_accelerate_config.py b/tests/test_cli_accelerate_config.py
new file mode 100644
index 00000000000..f869e9809ef
--- /dev/null
+++ b/tests/test_cli_accelerate_config.py
@@ -0,0 +1,56 @@
+# Copyright 2020-2026 The HuggingFace Team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import pytest
+
+from trl.cli.accelerate_config import resolve_accelerate_config_argument
+
+
+class TestResolveAccelerateConfigArgument:
+    def test_two_token_form(self):
+        """`--accelerate_config <name>` is resolved into `--config_file <path>`."""
+        result = resolve_accelerate_config_argument(["--accelerate_config", "single_gpu", "--num_processes", "1"])
+        assert result[0] == "--config_file"
+        assert result[1].endswith("single_gpu.yaml")
+        assert result[2:] == ["--num_processes", "1"]
+
+    def test_equals_form(self):
+        """`--accelerate_config=<name>` (equals-sign form) is resolved the same way as the two-token form."""
+        result = resolve_accelerate_config_argument(["--accelerate_config=single_gpu", "--num_processes", "1"])
+        assert result[0] == "--config_file"
+        assert result[1].endswith("single_gpu.yaml")
+        assert result[2:] == ["--num_processes", "1"]
+
+    def test_equals_form_matches_two_token_form(self):
+        """Both syntaxes should resolve to the exact same launch arguments."""
+        equals_form = resolve_accelerate_config_argument(["--accelerate_config=single_gpu", "--foo", "bar"])
+        two_token_form = resolve_accelerate_config_argument(["--accelerate_config", "single_gpu", "--foo", "bar"])
+        assert equals_form == two_token_form
+
+    def test_no_accelerate_config_argument(self):
+        """When `--accelerate_config` isn't present, the arguments are returned unchanged."""
+        args = ["--foo", "bar"]
+        assert resolve_accelerate_config_argument(args) == args
+
+    def test_missing_value_raises(self):
+        """`--accelerate_config` with no value after it raises a clear error."""
+        with pytest.raises(ValueError, match="Expected a value after `--accelerate_config`"):
+            resolve_accelerate_config_argument(["--accelerate_config"])
+
+    def test_invalid_config_name_raises(self):
+        """An unknown config name (and not a file) raises a clear error, for both syntaxes."""
+        with pytest.raises(ValueError, match="is neither a file nor a valid config"):
+            resolve_accelerate_config_argument(["--accelerate_config", "does_not_exist"])
+        with pytest.raises(ValueError, match="is neither a file nor a valid config"):
+            resolve_accelerate_config_argument(["--accelerate_config=does_not_exist"])
diff --git a/trl/cli/accelerate_config.py b/trl/cli/accelerate_config.py
index d775fca787f..2533c3ef2ec 100644
--- a/trl/cli/accelerate_config.py
+++ b/trl/cli/accelerate_config.py
@@ -21,8 +21,17 @@ def resolve_accelerate_config_argument(launch_args: list[str]) -> list[str]:
     Resolve `--accelerate_config` from CLI arguments into `accelerate --config_file`.
 
     The function supports either a filesystem path or a predefined config name shipped in `trl/accelerate_configs`
-    (without the `.yaml` suffix).
+    (without the `.yaml` suffix). Both the two-token form (`--accelerate_config single_gpu`) and the `=`-joined form
+    (`--accelerate_config=single_gpu`) are supported.
     """
+    # Normalize the `--accelerate_config=<value>` form into the two-token `--accelerate_config <value>` form so the
+    # rest of the function only has to handle a single case.
+    for index, arg in enumerate(launch_args):
+        if arg.startswith("--accelerate_config="):
+            config_name = arg.split("=", 1)[1]
+            launch_args = launch_args[:index] + ["--accelerate_config", config_name] + launch_args[index + 1 :]
+            break
+
     if "--accelerate_config" not in launch_args:
         return launch_args