Verified answer

No, That is considered a closed "Loop Cruise" and if you are a US citizen or LPR you do NOT need a Passport

Please see the link

Jim and Charlie are correct if you Start in the United States and return to the United States on the Cruise Liner. If you get off and fly back from Cozumel, then the answer is you will need a passport.

So to be on the safe side, carry the passport with you just in case of an emergency back home.

If you are on a "closed loop" cruise, no. "Closed loop" means a cruise that departs and returns to the same US port. For all other cruises, and to travel to Mexico in any other way, does require a US passport. You can find the requirements on the US State Department web site, which is http://www.state.gov./ Happy travel!

Jim is right...closed loop cruises do not require a passport. Your cruise line can confirm this, too.

Yes