Geary, who last pitched in the big leagues with the Astros in 2009, will report to the Padres' Spring Training facility on March 4.
His deal does not include an invitation to big league camp.
Geary, 34, attended Grossmont High in the San Diego suburb of El Cajon, Calif., and pitched for Mesa College. He has a 16-10 record and 3.92 ERA in 287 Major League career games, all coming as a reliever for the Phillies and Astros.
He was 7-1 with a 2.96 ERA in 81 games for the Phillies in 2006. He had a 2.53 ERA in 55 relief appearances with the Astros in '08.
Geary spent last season in the Minor Leagues, splitting time between Oklahoma City (4-5, 5.37 ERA) and Albuquerque (0-1, 5.06).
The Padres also released infielder Gregorio Petit, who suffered a major knee injury during winter ball and won't play this season. Petit signed a Minor League contract with the team in the offseason and was given an invitation to camp this spring.