diff --git a/litellm/constants.py b/litellm/constants.py
index 5c4fba50e1d..1c08fc5590b 100644
--- a/litellm/constants.py
+++ b/litellm/constants.py
@@ -186,7 +186,9 @@ MCP_PER_USER_TOKEN_EXPIRY_BUFFER_SECONDS: Final = int(os.getenv("MCP_PER_USER_TO
 
 # MCP timeout defaults (seconds). Override via env vars for slow/custom MCP servers.
 MCP_CLIENT_TIMEOUT: Final = float(os.getenv("LITELLM_MCP_CLIENT_TIMEOUT", "60.0"))
-MCP_MAX_SSE_EVENT_SIZE_BYTES: Final = get_env_int("LITELLM_MCP_MAX_SSE_EVENT_SIZE_BYTES", 64 * 1024 * 1024)
+MCP_MAX_SSE_EVENT_SIZE_BYTES: Final = get_env_int_in_range(
+    "LITELLM_MCP_MAX_SSE_EVENT_SIZE_BYTES", 64 * 1024 * 1024, 1, sys.maxsize
+)
 MCP_TOOL_LISTING_TIMEOUT: Final = float(os.getenv("LITELLM_MCP_TOOL_LISTING_TIMEOUT", "30.0"))
 MCP_METADATA_TIMEOUT: Final = float(os.getenv("LITELLM_MCP_METADATA_TIMEOUT", "10.0"))
 MCP_HEALTH_CHECK_TIMEOUT: Final = float(os.getenv("LITELLM_MCP_HEALTH_CHECK_TIMEOUT", "10.0"))
diff --git a/tests/unit/test_constants.py b/tests/unit/test_constants.py
index 12e473f68a4..21b75ceed76 100644
--- a/tests/unit/test_constants.py
+++ b/tests/unit/test_constants.py
@@ -1,3 +1,4 @@
+import sys
 import ast
 import inspect
 import json
@@ -68,3 +69,30 @@ def _build_constant_env_var_map() -> dict[str, str]:
             env_var_map[constant_name] = env_var_name
 
     return env_var_map
+
+
+@pytest.mark.parametrize(
+    ("raw", "expected"),
+    (
+        (None, 64 * 1024 * 1024),
+        ("", 64 * 1024 * 1024),
+        ("invalid", 64 * 1024 * 1024),
+        ("0", 64 * 1024 * 1024),
+        ("-1", 64 * 1024 * 1024),
+        ("1", 1),
+        ("200000", 200000),
+        (str(sys.maxsize), sys.maxsize),
+        (str(sys.maxsize + 1), 64 * 1024 * 1024),
+    ),
+)
+def test_mcp_sse_event_limit_uses_positive_override_or_default(raw: str | None, expected: int) -> None:
+    try:
+        with pytest.MonkeyPatch.context() as environment:
+            if raw is None:
+                environment.delenv("LITELLM_MCP_MAX_SSE_EVENT_SIZE_BYTES", raising=False)
+            else:
+                environment.setenv("LITELLM_MCP_MAX_SSE_EVENT_SIZE_BYTES", raw)
+            importlib.reload(constants)
+            assert constants.MCP_MAX_SSE_EVENT_SIZE_BYTES == expected
+    finally:
+        importlib.reload(constants)