diff --git a/litellm/litellm_core_utils/llm_request_utils.py b/litellm/litellm_core_utils/llm_request_utils.py
new file mode 100644
index 000000000..cd371ee1d
--- /dev/null
+++ b/litellm/litellm_core_utils/llm_request_utils.py
@@ -0,0 +1,30 @@
+from typing import Dict, Optional
+
+from langfuse.model import TextPromptClient
+
+
+def _ensure_extra_body_is_safe(extra_body: Optional[Dict]) -> Optional[Dict]:
+    """
+    Ensure that the extra_body sent in the request is safe,  otherwise users will see this error
+
+    "Object of type TextPromptClient is not JSON serializable
+
+
+    Relevant Issue: https://github.com/BerriAI/litellm/issues/4140
+    """
+    if extra_body is None:
+        return None
+
+    if not isinstance(extra_body, dict):
+        return extra_body
+
+    if "metadata" in extra_body and isinstance(extra_body["metadata"], dict):
+        if "prompt" in extra_body["metadata"]:
+            _prompt = extra_body["metadata"].get("prompt")
+
+            # users can send Langfuse TextPromptClient objects, so we need to convert them to dicts
+            # Langfuse TextPromptClients have .__dict__ attribute
+            if _prompt is not None and hasattr(_prompt, "__dict__"):
+                extra_body["metadata"]["prompt"] = _prompt.__dict__
+
+    return extra_body
diff --git a/litellm/utils.py b/litellm/utils.py
index eac07c550..795526a32 100644
--- a/litellm/utils.py
+++ b/litellm/utils.py
@@ -50,6 +50,7 @@ import litellm._service_logger  # for storing API inputs, outputs, and metadata
 import litellm.litellm_core_utils
 from litellm.caching import DualCache
 from litellm.litellm_core_utils.core_helpers import map_finish_reason
+from litellm.litellm_core_utils.llm_request_utils import _ensure_extra_body_is_safe
 from litellm.litellm_core_utils.redact_messages import (
     redact_message_input_output_from_logging,
 )
@@ -3256,6 +3257,10 @@ def get_optional_params(
                 extra_body[k] = passed_params[k]
         optional_params.setdefault("extra_body", {})
         optional_params["extra_body"] = {**optional_params["extra_body"], **extra_body}
+
+        optional_params["extra_body"] = _ensure_extra_body_is_safe(
+            extra_body=optional_params["extra_body"]
+        )
     else:
         # if user passed in non-default kwargs for specific providers/models, pass them along
         for k in passed_params.keys():