diff --git a/litellm/litellm_core_utils/get_llm_provider_logic.py b/litellm/litellm_core_utils/get_llm_provider_logic.py
index 36218417377..a79dcfe98c6 100644
--- a/litellm/litellm_core_utils/get_llm_provider_logic.py
+++ b/litellm/litellm_core_utils/get_llm_provider_logic.py
@@ -158,12 +158,15 @@ def get_llm_provider(  # noqa: PLR0915
         ):  # handle scenario where model="azure/*" and custom_llm_provider="azure"
             model = custom_llm_provider + "/" + model
 
-        # Native OpenRouter models have IDs like "openrouter/free" where the
+        # Native OpenRouter models have IDs like "openrouter/auto" where the
         # "openrouter/" prefix is part of the actual model name on the API.
-        # When called from a bridge (e.g. anthropic_messages adapter),
-        # custom_llm_provider is already resolved, so return early to prevent
-        # the provider-list stripping below from removing the prefix.
-        if custom_llm_provider == "openrouter" and model.startswith("openrouter/"):
+        # Only preserve prefix for single-segment native models (no extra '/'),
+        # not for provider-routed models like "openrouter/anthropic/claude-3.5-sonnet".
+        if (
+            custom_llm_provider == "openrouter"
+            and model.startswith("openrouter/")
+            and "/" not in model[len("openrouter/") :]
+        ):
             return model, custom_llm_provider, dynamic_api_key, api_base
 
         if api_key and api_key.startswith("os.environ/"):
diff --git a/tests/local_testing/test_get_llm_provider.py b/tests/local_testing/test_get_llm_provider.py
index 9b07111ea54..019b938842c 100644
--- a/tests/local_testing/test_get_llm_provider.py
+++ b/tests/local_testing/test_get_llm_provider.py
@@ -420,3 +420,19 @@ def test_get_llm_provider_use_proxy_arg_true_with_direct_args():
     assert provider == "litellm_proxy"
     assert key == arg_api_key  # Should use the argument key
     assert base == arg_api_base # Should use the argument base
+
+
+def test_openrouter_model_prefix_stripped():
+    """
+    GH#24234: OpenRouter models like "openrouter/anthropic/claude-3.5-sonnet"
+    should have the "openrouter/" prefix stripped before being sent to the API.
+    The API expects "anthropic/claude-3.5-sonnet", not the full prefixed name.
+    """
+    model, provider, _, _ = litellm.get_llm_provider(
+        model="openrouter/anthropic/claude-3.5-sonnet"
+    )
+    assert provider == "openrouter"
+    assert model == "anthropic/claude-3.5-sonnet", (
+        f"Expected 'anthropic/claude-3.5-sonnet' but got '{model}'. "
+        "The 'openrouter/' prefix was not stripped."
+    )