Loaiza, a two-time All-Star, had made only two starts after missing the first 4½ months of the season because of three different injuries. He allowed just three earned runs in 14 2/3 innings in the two starts and gives the Dodgers' depleted rotation a boost for the stretch run.
"I never thought I would get traded," Loaiza said before leaving Oakland. "I didn't think this was going to happen but it happened. I feel kind of shocked because I had just started two games this year."
Loaiza will join the Dodgers for their weekend series in San Diego. Los Angeles began the day 4½ games behind Arizona in the NL West and 3½ games behind San Diego in the wild-card race.
"I've been there before, with the Yankees and with this team last year," Loaiza said of his postseason experience. "I know what it takes to win."
Los Angeles signed David Wells last week as general manager Ned Colletti tries to overcome injuries to Jason Schmidt, Randy Wolf and Hong-Chih Kuo and ineffectiveness by Brett Tomko and Mark Hendrickson.
"At this time of the year, we're looking for any way to improve the team and Esteban is a talented veteran who we hope can contribute down the stretch and next season," Colletti said. "He has a history of winning games and right now that's what's most important to our team."
The Dodgers assume the $1.17 million Loaiza is owed for the rest of this season, as well as his $6.5 million salary for 2008. Loaiza, 35, also has a $7.5 million club option for 2009 with a $375,000 buyout. Oakland still owes Loaiza $1 million from his signing bonus.
"Certainly Esteban was making some money next year," A's assistant general manager David Forst said. "But it wasn't as much about salary as about giving guys an opportunity."
The A's have not decided who will take Loaiza's spot in the rotation Sunday against Detroit. Looking ahead to next season, Oakland has Dan Haren, Joe Blanton, Chad Gaudin, Lenny DiNardo and the injury-plagued Rich Harden under its control, as well as younger pitchers like Dallas Braden and Dan Meyer.
"We felt like it was an opportunity for some of the younger guys in the organization going forward and it gives us some flexibility," Forst said. "Hopefully it works out well for Esteban. He's going to a team trying to win a division."
Loaiza has a 124-108 career record and 4.60 ERA in 362 career games for the Pirates, Rangers, Blue Jays, White Sox, Yankees, Nationals and Athletics.
To make room for Loaiza on the 40-man roster, the Dodgers transferred outfielder Jason Repko to the 60-day disabled list.
Oakland recalled right-hander Colby Lewis from Triple-A Sacramento to take Loaiza's place on the roster.