diff --git a/litellm/litellm_core_utils/litellm_logging.py b/litellm/litellm_core_utils/litellm_logging.py
index 9e0461e951d..fc28847682e 100644
--- a/litellm/litellm_core_utils/litellm_logging.py
+++ b/litellm/litellm_core_utils/litellm_logging.py
@@ -7108,13 +7108,18 @@ class StandardLoggingPayloadSetup:
         headers: Final = proxy_server_request.get("headers", {})
         if not isinstance(headers, dict):
             return None
-        request_headers: Final = cast(  # cast-ok: request headers are untyped framework data
-            dict[str, str], headers
-        )
 
-        header_tags: Final = []
+        # Headers are case-insensitive per RFC 7230 / RFC 9110.
+        # Normalize header keys to lowercase to ensure tags are captured regardless of request casing.
+        normalized_headers: Final[dict[str, str]] = {
+            str(k).lower(): str(v)
+            for k, v in headers.items()
+            if v is not None
+        }
+
+        header_tags: Final[list[str]] = []
         for header_name in extra_headers:
-            header_value = request_headers.get(header_name)
+            header_value = normalized_headers.get(header_name.lower())
             if header_value:
                 header_tags.append(f"{header_name}: {header_value}")
 
diff --git a/tests/unit/litellm_core_utils/test_litellm_logging.py b/tests/unit/litellm_core_utils/test_litellm_logging.py
index 561ac9b2b33..8646bd2d52d 100644
--- a/tests/unit/litellm_core_utils/test_litellm_logging.py
+++ b/tests/unit/litellm_core_utils/test_litellm_logging.py
@@ -3662,6 +3662,21 @@ def test_get_extra_header_tags():
         assert "x-custom: my-value" in result
         assert "x-empty:" not in str(result)
 
+        # Test case 8: Case-insensitive header matching (RFC 7230 / RFC 9110)
+        litellm.extra_spend_tag_headers = ["x-session-id", "X-Organization-ID"]
+        result = StandardLoggingPayloadSetup._get_extra_header_tags(
+            proxy_server_request={
+                "headers": {
+                    "X-Session-Id": "sess_123",
+                    "x-organization-id": "org_456",
+                }
+            }
+        )
+        assert result is not None
+        assert len(result) == 2
+        assert "x-session-id: sess_123" in result
+        assert "X-Organization-ID: org_456" in result
+
     finally:
         # Restore original value
         if original_extra_headers is not None: