Merchant Mariner Credential (MMC): How to Apply
The Merchant Mariner Credential, or MMC, is the core U.S. Coast Guard document for anyone sailing aboard a commercial vessel. It documents your identity and every qualification, rating, license, and endorsement (including STCW) you hold, all in one credential.
Who needs one
Anyone working aboard a vessel as part of the required crew, from an entry-level unlicensed deckhand to a licensed captain or engineer, needs an MMC. Which specific rating or license you apply for depends on the job and your sea time and training background.
How to apply
Applications go through the U.S. Coast Guard's National Maritime Center (NMC). The process generally involves documenting sea time, completing required training, passing a USCG medical evaluation, and in some cases exams. Because requirements vary significantly by rating or license type, review the current process directly on the National Maritime Center's site (opens in new tab) for the specific credential you're pursuing.
Renewal and upgrades
MMCs are renewed periodically, and merchant mariners often upgrade their credential over time by adding endorsements or moving from unlicensed ratings to licensed positions as they accumulate sea time and additional training.
Frequently Asked Questions
Do I need an MMC to work on a boat?
If you're sailing aboard a vessel in a position that counts toward the crew, whether unlicensed or licensed, you generally need an MMC. Shoreside-only roles usually don't require one.
What's the difference between an MMC rating and a license?
A rating (like Able Seaman or Qualified Member of the Engine Department) is for unlicensed crew positions. A license (like a deck or engineering officer license) is for positions with command or watchstanding authority and requires more sea time and testing.
How long does the MMC application take?
Processing time varies based on application completeness and the National Maritime Center's current workload. Check current processing times directly on the NMC's website rather than assuming a fixed timeline.