The sides had agreed to terms in December. Mota has been added to the 40-man roster. Mota, a 38-year-old right-hander, has become a reliable option for manager Bruce Bochy. He went 2-2 with a 3.81 ERA in 52 outings last season for the NL West runners-up.
Mota's 80 1/3 innings last season were his third highest in 13 big league seasons and most since 2004, when he pitched for the Los Angeles Dodgers and the Marlins.
Mota made one appearance against Texas during the 2010 World Series, when the Giants wrapped up the franchise's first championship since moving West in 1958.