The Dodgers, who claimed Barajas on waivers, exchanged cash for the catcher, who turns 35 on Sept. 1. He had a .263 on-base percentage and .414 slugging percentage in 267 plate appearances with New York this season. He came off the 15-day disabled list Thursday after being sidelined with a strained left oblique.
He is set to join the team on Tuesday in Milwaukee, where they open a three-game series.
The Dodgers, who lost starting catcher Russell Martin for the season Aug. 3 with injuries to his right hip, have been trying to get by with Brad Ausmus and A.J. Ellis., neither of whom have slugging percentages above .250.
Initially, Barajas is expected to become the Dodgers' primary catcher. Ausmus -- who is retiring after the season -- will return to the backup role.
Ellis will be optioned to Triple-A Albuquerque to clear a roster spot for Barajas. But Ellis will be recalled for the September roster expansion, after which the Dodgers plan to carry three catchers for the rest of the season.
"We'll play it by ear [on playing time],'' Dodgers manager Joe Torre said. ''At this point in time, we needed that third catcher, because when September 1 comes, we would have been hard-pressed to find another catcher to bring up. He will share with Ausmus, but he will probably do most of the catching.''
Barajas has played for Arizona, Texas, Philadelphia, Toronto and the Mets during his career that began in 1999. He has hit 104 career homers, including a career-high 21 with Texas in 2005.
The Mets promoted Jesus Feliciano from Triple-A Buffalo to take Barajas' place on the roster. Feliciano hit .342 with one homer and 26 RBIs in 78 games for Buffalo.
Tony Jackson and Jon Weisman of ESPNLosAngeles.com, Adam Rubin of ESPNNewYork.com and The Associated Press contributed to this report.