How to Verify a Merchant Mariner Credential

What a Merchant Mariner Credential contains

The MMC is a single document that combines what were previously separate licenses and documents. It includes:

• Officer Endorsements: Captain, Mate, Chief Engineer, Engineer, Pilot — based on tonnage, waters, and vessel type
• Rating Endorsements: Able Seaman (AB), Ordinary Seaman (OS), Wiper, Oiler, Steward — non-officer deck and engine ratings
• Tankerman Endorsements: PIQ (Person in Charge) endorsements for liquid cargo operations
• STCW Endorsements: International certifications required under the International Convention on Standards of Training, Certification and Watchkeeping (STCW)

The MMC is issued for 5 years. STCW endorsements within the MMC may have different renewal cycles — verify each endorsement's validity separately when the role involves international voyages.

USCG NMC credential verification

The USCG National Maritime Center maintains the Credential Holder Registry for all MMC holders.

Verify MMC credentials at: marinerlicensing.uscg.mil → Credential Holder Search (search by name or MMC number). Verification confirms:

• MMC holder name and credential number
• All active endorsements (officer, rating, STCW, tankerman)
• MMC expiration date
• Any suspended, revoked, or surrendered endorsements

Suspension and revocation actions are recorded in the NMC registry. Review the full record, not just the MMC expiration date.

STCW endorsements for international voyages

Mariners serving on vessels making international voyages must hold STCW-compliant certifications. The STCW Convention (as amended by the Manila Amendments) requires specific training and endorsements:

• STCW Basic Safety Training: Personal survival, fire prevention and firefighting, elementary first aid, personal safety and social responsibilities
• STCW Advanced Training: Advanced firefighting, medical first aid, etc. — required for certain officer and rating positions
• Management Level Certificates: STCW officer of the watch (OOW), chief mate, master endorsements for vessels over 500 GT on international voyages

STCW endorsements are included in the MMC and visible in the NMC verification portal. Confirm that all required STCW endorsements are present and current for the vessel's trade route.

TWIC (Transportation Worker Identification Credential)

The Transportation Worker Identification Credential (TWIC) is required for unescorted access to secure areas of maritime facilities and vessels regulated under the Maritime Transportation Security Act (MTSA). TWIC is separate from the MMC — a mariner may hold an MMC without a TWIC and vice versa.

TWIC is issued by the TSA (Transportation Security Administration). TWIC validity can be checked by the cardholder or the employer using the TWIC Continuous Evaluation or TWIC Reader programs.

For positions working in MTSA-regulated facilities or vessels, confirm the mariner holds a valid TWIC in addition to the MMC.

Drug testing requirements

Mariners aboard documented vessels are subject to USCG and DOT chemical testing regulations under 46 CFR Part 16. Employers must maintain compliant drug and alcohol testing programs. The employer — not the mariner — is responsible for maintaining testing records, but verifying compliance is part of maritime credential verification.

Verification checklist