diff --git a/litellm/proxy/common_request_processing.py b/litellm/proxy/common_request_processing.py
index e812b03385d..c1701724c92 100644
--- a/litellm/proxy/common_request_processing.py
+++ b/litellm/proxy/common_request_processing.py
@@ -286,6 +286,7 @@ from litellm.proxy.litellm_pre_call_utils import (
     LiteLLMProxyRequestSetup,
     add_litellm_data_to_request,
     get_metadata_variable_name,
+    redact_proxy_server_request_body_on_guardrail_block,
     refresh_proxy_server_request_body_snapshot,
     reject_url_valued_destination,
     sanitize_for_log,
@@ -2670,12 +2671,17 @@ class ProxyBaseLLMRequestProcessing:
         prefetch_model = self.data.get("model")
         if llm_router is not None and isinstance(prefetch_model, str):
             RoutingContext(llm_router).arm_read_prefetch(prefetch_model, self.data)
-        self.data = await proxy_logging_obj.pre_call_hook(
-            user_api_key_dict=user_api_key_dict,
-            data=self.data,
-            call_type=route_type,
-            skip_guardrails=skip_guardrails,
-        )
+        try:
+            self.data = await proxy_logging_obj.pre_call_hook(
+                user_api_key_dict=user_api_key_dict,
+                data=self.data,
+                call_type=route_type,
+                skip_guardrails=skip_guardrails,
+            )
+        except Exception:
+            if isinstance(self.data, dict):
+                redact_proxy_server_request_body_on_guardrail_block(self.data)
+            raise
         await _enforce_guardrail_added_tag_budgets(
             data=self.data,
             tags_before_guardrails=self._tags_before_guardrails,
diff --git a/litellm/proxy/litellm_pre_call_utils.py b/litellm/proxy/litellm_pre_call_utils.py
index 4444d6d25f9..6a83e17f52b 100644
--- a/litellm/proxy/litellm_pre_call_utils.py
+++ b/litellm/proxy/litellm_pre_call_utils.py
@@ -2608,6 +2608,26 @@ def refresh_proxy_server_request_body_snapshot(
         )
 
 
+def redact_proxy_server_request_body_on_guardrail_block(
+    data: MutableMapping[str, object],
+) -> None:
+    """
+    Redact prompt/messages fields in data['proxy_server_request']['body'] when a pre-call
+    guardrail blocks a request (#50127).
+    This ensures that raw PII or secret content that triggered a guardrail rejection is not
+    persisted in plain text in LiteLLM_SpendLogs via async_post_call_failure_hook.
+    """
+    proxy_server_request: Final = data.get("proxy_server_request")
+    if not isinstance(proxy_server_request, dict):
+        return
+    body: Final = proxy_server_request.get("body")
+    if not isinstance(body, dict):
+        return
+    for field in ("messages", "prompt", "input"):
+        if field in body:
+            body[field] = "[REDACTED - BLOCKED BY GUARDRAIL]"
+
+
 async def add_litellm_data_to_request(
     data: dict,
     request: Request,
diff --git a/tests/unit/proxy/test_litellm_pre_call_utils.py b/tests/unit/proxy/test_litellm_pre_call_utils.py
index 91c87c63067..a0f8043b8f7 100644
--- a/tests/unit/proxy/test_litellm_pre_call_utils.py
+++ b/tests/unit/proxy/test_litellm_pre_call_utils.py
@@ -1391,6 +1391,37 @@ def test_refresh_proxy_server_request_body_snapshot_picks_up_guardrail_masking()
     assert "123-45-6789" not in json.dumps(refreshed_body)
 
 
+def test_redact_proxy_server_request_body_on_guardrail_block():
+    """
+    Regression: When a pre-call guardrail blocks a request (e.g. secret or PII detected),
+    pre_call_hook raises an exception. The raw snapshot in proxy_server_request['body']
+    must be redacted so raw blocked text is not written into SpendLogs in plain text (#50127).
+    """
+    from litellm.proxy.litellm_pre_call_utils import (
+        redact_proxy_server_request_body_on_guardrail_block,
+    )
+
+    data = {
+        "model": "gpt-4",
+        "messages": [{"role": "user", "content": "secret password is supersecret"}],
+        "proxy_server_request": {
+            "url": "http://localhost/v1/chat/completions",
+            "body": {
+                "model": "gpt-4",
+                "messages": [{"role": "user", "content": "secret password is supersecret"}],
+                "prompt": "supersecret prompt",
+            },
+        },
+    }
+
+    redact_proxy_server_request_body_on_guardrail_block(data)
+
+    body = data["proxy_server_request"]["body"]
+    assert body["messages"] == "[REDACTED - BLOCKED BY GUARDRAIL]"
+    assert body["prompt"] == "[REDACTED - BLOCKED BY GUARDRAIL]"
+    assert "supersecret" not in json.dumps(body)
+
+
 @pytest.mark.asyncio
 async def test_add_litellm_data_to_request_strips_string_encoded_admin_injection():
     """Regression: metadata arriving as a JSON string (multipart/form-data or