A representative of the Guinness Book of World Records, Stuart Claxton, made it official at the International Mariachi Festival.
The old record belonged to 520 mariachis who performed in San Antonio, Texas, in 2007, said Francisco Beckman, an organizer of the record-breaking attempt.
Record-breaking is all the rage in Mexico.
On Saturday, thousands in Mexico City claimed they put on the largest "Thriller" dance by people performing simultaneously in one place. The Guinness official at that event said a decision on whether they did will be made in a week.
Mexico also boasted the world's biggest cheesecake and group kiss earlier this year.
