Los Angeles received right-handed reliever Brian Stokes, a native Californian, in exchange for Matthews, who had slumped for three straight seasons since signing a $50 million, five-year contract.
"He voiced his frustration to us because of his desire to play every day," Angels manager Mike Scioscia said.
New York wanted another outfielder after Carlos Beltran had knee surgery last week. Beltran, sidelined for much of last season, is not expected back until May, and Matthews will compete with Angel Pagan to play center field while Beltran is on the disabled list.
"I think it's going to be open competition," Mets general manager Omar Minaya said. "Nobody's going to be given the job."
Matthews is owed salaries of $11 million this year and $12 million in 2011, plus a $500,000 bonus for getting traded. The Mets will pay just $1 million per season, and the Angels will give New York money to cover the remainder of the salary plus the bonus, a person familiar with the details told The Associated Press. The person spoke on condition of anonymity because the financial details were not announced.
Matthews hit .313 with 19 homers and 79 RBIs for Texas in 2006, when he made the AL All-Star team, then signed the big deal with the Angels that turned out to be the worst contract in the team's history. He slumped to a .252 average with 18 homers and 72 RBIs during his first season in Anaheim, then lost his center field job when the Angels signed Torii Hunter.
"It obviously wasn't the role that Gary was looking for," Scioscia said, adding that Matthews' disappointment was understandable. "To say that Gary was a disruptive influence or was not happy in our clubhouse is 180 degrees from the situation."
Matthews had 46 RBIs in 2008 and 50 last year, when he started 80 games. Now 35, he is the son of Gary Matthews, the 1973 NL Rookie of the Year.
"It's an opportunity for him to come into New York and be able to hopefully get more playing time," Minaya said.
Matthews was briefly with the Mets but got only one at-bat for New York -- he fouled out against Pittsburgh's Mike Lincoln as a pinch hitter. The Mets purchased him from the Pirates in December 2001, then traded him to Baltimore for left-hander John Bale.
SI.com reported in February 2007 that Matthews was sent human growth hormone by Applied Pharmacy in August 2004, an accusation he denied. Major League Baseball concluded there was insufficient evidence to discipline him.
New York added Matthews after failing to land two of its free-agent targets: catcher Bengie Molina, who decided to stay with San Francisco, and pitcher Joel Pineiro, who agreed to a $16 million, two-year contract with the Angels.
"You always wish that when you put (out) these offers, you're able to get the players," Minaya said.
The 30-year-old Stokes, born in Pomona, was 2-4 with a 3.97 ERA out of the bullpen last season, setting career highs for games (69) and innings (70 1-3). He spent the last two seasons with the Mets after making his big league debut for Tampa Bay.
"Being from Southern California growing up, I think this is going to be awesome for me," he said.
While the Angels haven't confirmed Pineiro's agreement, Scioscia already was referring to him as a member of the team.
"I think that depth moving forward is something that we need to re-establish," he said. "I think Brian is going to go a long way to help us in that department, and I think gives us, along with the acquisition of Joel Pineiro, some versatility between our rotation and our bullpen."