Staff

A Second Mate is a position held by a member of a crew. He is the second highest ranked officer on a crew outside the captain, the first being the First Mate.

Role and Duties
The Second Mate's duty is similar to the First Mate's and they will often share responsibilities on the ship. He is the next in line to take over as captain after the First Mate.

In One Piece
Cabaji is the second mate on Buggy's crew. Oddly enough, he seems to pull more favor with the captain and pull more weight with the crew, having as Mohji the first mate. Cabaji is the first and so far the only confirmed second mate to appear in the series.

Translation and Dub Issues
Due to a mistranslation within the VIZ Media, Pearl of the Krieg Pirates was mislabeled as a Second Mate, but in truth he is the commander of the second division of the crew.

Trivia

 * Among the Straw Hat Pirates, some people believe Sanji, the chef of the crew, is the second mate; as he sometimes share some duties with Zoro, who is often considered the first mate. It should be noted that duties are shared with other crew members as well. Both Nami and Usopp have given orders and had them followed. Luffy has not appointed anyone to the station, but the Straw Hats also do not officially have a "First Mate" to begin with.