Police were not releasing the name of the man from Malin International Ship Repair, according to the Houston Chronicle.
The accident happened on Thursday on the 2,900-dwt Western Monarch (built 1991).
The worker was on a ladder about 30 feet above the deck at the time.
He lost his balance and fell, striking his head on a beam.
An investigation has begun.
The vessel is operated by WesternGeco of the UK.
