Larranaga, 36, will be an assistant coach with the Celtics, Adrian Wojnarowski of Yahoo! Sports reports. He spent last season as the coach of the Erie Bayhawks in the NBA Development League, where he coached Jeremy Lin for one game, when the then-unknown point guard recorded a triple-double against the Maine Red Claws.
Larranaga was born in New York City and played college basketball Bowling Green State, but was a member of Ireland's national team. He played for 12 years for various teams in Europe.
The Larranaga name is well-known in coaching thanks to James Larranaga, who led George Mason to the 2006 Final Four. James, now the head coach at the University of Miami, is Larranaga's father.