diff --git a/tests/v1/engine/test_engine_core_client.py b/tests/v1/engine/test_engine_core_client.py
index 770560a5e549e..8c840fd2ac7e0 100644
--- a/tests/v1/engine/test_engine_core_client.py
+++ b/tests/v1/engine/test_engine_core_client.py
@@ -2,12 +2,14 @@
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
 import asyncio
+import importlib
 import os
 import signal
 import time
 import uuid
 from dataclasses import dataclass
 from threading import Thread
+from types import SimpleNamespace
 from typing import Any
 from unittest.mock import MagicMock
 
@@ -24,7 +26,11 @@ from vllm.usage.usage_lib import UsageContext
 from vllm.utils.torch_utils import set_default_torch_num_threads
 from vllm.v1.engine import EngineCoreRequest
 from vllm.v1.engine.core import EngineCore
-from vllm.v1.engine.core_client import AsyncMPClient, EngineCoreClient, SyncMPClient
+from vllm.v1.engine.core_client import (
+    AsyncMPClient,
+    EngineCoreClient,
+    SyncMPClient,
+)
 from vllm.v1.engine.utils import CoreEngineProcManager
 from vllm.v1.executor.abstract import Executor
 
@@ -60,6 +66,91 @@ def make_request(
     )
 
 
+def _reload_envs_module():
+    import vllm.envs as envs_mod
+
+    cache_clear = getattr(getattr(envs_mod, "__getattr__", None), "cache_clear", None)
+    if cache_clear is not None:
+        cache_clear()
+    return importlib.reload(envs_mod)
+
+
+def _reload_core_client_module():
+    module = importlib.import_module("vllm.v1.engine.core_client")
+    return importlib.reload(module)
+
+
+def test_mp_client_uses_env_timeout(monkeypatch: pytest.MonkeyPatch):
+    timeout_value = 654
+    monkeypatch.setenv("VLLM_ENGINE_READY_TIMEOUT_S", str(timeout_value))
+
+    # Ensure that the environment variable is loaded if caching is enabled
+    _reload_envs_module()
+    core_client_mod = _reload_core_client_module()
+
+    poll_timeouts: list[int] = []
+
+    class ShadowSocket:
+        def poll(self, timeout: int) -> int:
+            # Capture the timeout value for each poll call
+            poll_timeouts.append(timeout)
+            return 1
+
+        def recv_multipart(self):
+            return (b"\x00\x00", b"ready")
+
+    class DummySocket:
+        def send_multipart(self, _msg, *, copy: bool = False, track: bool = False):
+            if track:
+                return SimpleNamespace(done=True)
+
+        def recv_multipart(self, *, copy: bool = False):
+            return (b"", b"")
+
+        def close(self, *, linger: int = 0):
+            pass
+
+        def bind(self, _address):
+            pass
+
+        def connect(self, _address):
+            pass
+
+        def setsockopt(self, *_args, **_kwargs):
+            pass
+
+    monkeypatch.setattr(core_client_mod.zmq.Socket, "shadow", lambda *_: ShadowSocket())
+    monkeypatch.setattr(
+        core_client_mod, "make_zmq_socket", lambda *_, **__: DummySocket()
+    )
+
+    parallel_config = SimpleNamespace(
+        data_parallel_size=1,
+        data_parallel_rank=0,
+        data_parallel_size_local=1,
+        data_parallel_rank_local=None,
+        data_parallel_hybrid_lb=False,
+        data_parallel_external_lb=False,
+    )
+    vllm_config = SimpleNamespace(parallel_config=parallel_config)
+
+    client = core_client_mod.MPClient(
+        asyncio_mode=False,
+        vllm_config=vllm_config,
+        executor_class=object,
+        log_stats=False,
+        client_addresses={
+            "input_address": "inproc://input",
+            "output_address": "inproc://output",
+        },
+    )
+    try:
+        # timeout_value is in seconds, but poll receives milliseconds
+        assert poll_timeouts == [timeout_value * 1000]
+    finally:
+        client.shutdown()
+
+
 def loop_until_done(client: EngineCoreClient, outputs: dict):
     while True:
         engine_core_outputs = client.get_output().outputs
diff --git a/vllm/envs.py b/vllm/envs.py
index f6db42e9124d6..1d4128d74b95c 100755
--- a/vllm/envs.py
+++ b/vllm/envs.py
@@ -24,6 +24,7 @@ if TYPE_CHECKING:
     LOCAL_RANK: int = 0
     CUDA_VISIBLE_DEVICES: str | None = None
     VLLM_ENGINE_ITERATION_TIMEOUT_S: int = 60
+    VLLM_ENGINE_READY_TIMEOUT_S: int = 600
     VLLM_API_KEY: str | None = None
     VLLM_DEBUG_LOG_API_SERVER_RESPONSE: bool = False
     S3_ACCESS_KEY_ID: str | None = None
@@ -604,6 +605,11 @@ environment_variables: dict[str, Callable[[], Any]] = {
     "VLLM_ENGINE_ITERATION_TIMEOUT_S": lambda: int(
         os.environ.get("VLLM_ENGINE_ITERATION_TIMEOUT_S", "60")
     ),
+    # Timeout in seconds for waiting for engine cores to become ready
+    # during startup. Default is 600 seconds (10 minutes).
+    "VLLM_ENGINE_READY_TIMEOUT_S": lambda: int(
+        os.environ.get("VLLM_ENGINE_READY_TIMEOUT_S", "600")
+    ),
     # API key for vLLM API server
     "VLLM_API_KEY": lambda: os.environ.get("VLLM_API_KEY", None),
     # Whether to log responses from API Server for debugging
diff --git a/vllm/v1/engine/core_client.py b/vllm/v1/engine/core_client.py
index 807db8275fbf5..cacbc805e84f8 100644
--- a/vllm/v1/engine/core_client.py
+++ b/vllm/v1/engine/core_client.py
@@ -20,6 +20,7 @@ import zmq
 import zmq.asyncio
 
 from vllm.config import VllmConfig
+from vllm.envs import VLLM_ENGINE_READY_TIMEOUT_S
 from vllm.logger import init_logger
 from vllm.lora.request import LoRARequest
 from vllm.tasks import SupportedTask
@@ -528,7 +529,9 @@ class MPClient(EngineCoreClient):
             identities = set(self.core_engines)
             sync_input_socket = zmq.Socket.shadow(self.input_socket)
             while identities:
-                if not sync_input_socket.poll(timeout=600_000):
+                if not sync_input_socket.poll(
+                    timeout=VLLM_ENGINE_READY_TIMEOUT_S * 1000  # convert to ms
+                ):
                     raise TimeoutError(
                         "Timed out waiting for engines to send"
                         "initial message on input socket."
@@ -1340,7 +1343,9 @@ class DPLBAsyncMPClient(DPAsyncMPClient):
         # Wait for ready messages from new engines on the input socket
         sync_input_socket = zmq.Socket.shadow(self.input_socket)
         while new_engine_identities:
-            if not sync_input_socket.poll(timeout=600_000):
+            if not sync_input_socket.poll(
+                timeout=VLLM_ENGINE_READY_TIMEOUT_S * 1000  # convert to ms
+            ):
                 raise TimeoutError(
                     "Timed out waiting for new engines to send initial "
                     "message on input socket."