diff --git a/.generator/cli.py b/.generator/cli.py
index 3e6075901fb8..4dc20c6b53cb 100644
--- a/.generator/cli.py
+++ b/.generator/cli.py
@@ -348,11 +348,22 @@ def _run_post_processor(output: str, library_id: str, is_mono_repo: bool):
     else:
         raise SYNTHTOOL_IMPORT_ERROR  # pragma: NO COVER
 
-    # If there is no noxfile, run `isort`` and `black` on the output.
+    # If there is no noxfile, run `ruff` on the output.
     # This is required for proto-only libraries which are not GAPIC.
     if not Path(f"{output}/{path_to_library}/noxfile.py").exists():
-        subprocess.run(["isort", output])
-        subprocess.run(["black", output])
+        # TODO(https://github.com/googleapis/google-cloud-python/issues/15538):
+        # Investigate if a `target_version needs to be maintained
+        # or can be eliminated.
+        target_version = "py37"
+        common_args = [
+            f"--target-version={target_version}",
+            "--line-length=88",
+        ]
+        # 1. Run Ruff to fix imports (replaces isort)
+        subprocess.run(["ruff", "check", "--select", "I", "--fix", *common_args], check=True)
+        
+        # 2. Run Ruff to format code (replaces black)
+        subprocess.run(["ruff", "format", *common_args], check=True)
 
     logger.info("Python post-processor ran successfully.")
 
diff --git a/.generator/requirements-test.in b/.generator/requirements-test.in
index 59ae478b8438..c72643d50d01 100644
--- a/.generator/requirements-test.in
+++ b/.generator/requirements-test.in
@@ -18,5 +18,4 @@ pytest-mock
 gcp-synthtool @ git+https://github.com/googleapis/synthtool@5aa438a342707842d11fbbb302c6277fbf9e4655
 starlark-pyo3>=2025.1
 build
-black==23.7.0
-isort==5.11.0
+ruff==0.14.14
diff --git a/.generator/requirements.in b/.generator/requirements.in
index b8811a286483..3f72f825ed5a 100644
--- a/.generator/requirements.in
+++ b/.generator/requirements.in
@@ -3,5 +3,4 @@ gapic-generator==1.30.7 # replace isort and black with ruff https://github.com/g
 nox
 starlark-pyo3>=2025.1
 build
-black==23.7.0
-isort==5.11.0
+ruff==0.14.14