A man travelling as a passenger in a truck has died as the vehicle collided with another truck.

The two trucks collided on Greystanes Rd at Greystanes in Western Sydney about 4.20am on Friday.

The man died at the scene of the crash and is yet to be formally identified.

Know the news with the 7NEWS app: Download today

The drivers of both trucks were not injured in the crash.

They were taken to Westmead Hospital for mandatory testing.

NSW Police are investigating the circumstances of the crash and urge anyone with relevant information to come forward.

Greystanes Rd is currently closed between Bathurst St and Old Prospect Rd, according to Live Traffic NSW.