diff --git a/litellm/utils.py b/litellm/utils.py
index dfacefe6971..53ab2d8eb6b 100644
--- a/litellm/utils.py
+++ b/litellm/utils.py
@@ -3453,7 +3453,28 @@ def get_optional_params_embeddings(  # noqa: PLR0915
         else:
             optional_params = non_default_params
     else:
-        optional_params = non_default_params
+        # openai_compatible_providers (e.g. hosted_vllm, openrouter, etc.)
+        # Pass all params through, but honour drop_params for `dimensions`
+        # because many vLLM / compatible endpoints don't support it and return
+        # 422 when it is present.  Only text-embedding-3-* models support it.
+        optional_params = non_default_params.copy()
+        if (
+            "dimensions" in optional_params
+            and model is not None
+            and "text-embedding-3" not in model
+        ):
+            if litellm.drop_params is True or drop_params is True:
+                optional_params.pop("dimensions")
+            else:
+                raise UnsupportedParamsError(
+                    status_code=500,
+                    message=(
+                        f"Setting 'dimensions' is not supported for model '{model}' "
+                        f"with provider '{custom_llm_provider}'. Only text-embedding-3-* "
+                        "models support this parameter. To drop it from the call, set "
+                        "`litellm.drop_params = True`."
+                    ),
+                )
 
     final_params = add_provider_specific_params_to_optional_params(
         optional_params=optional_params,