Pierre spent three-years in Los Angeles, where he batted .294 and often played as a late-game defensive replacement.
"Juan always put the Dodgers first, even when it wasn't in his personal best interest," Dodgers general manager Ned Colletti said Tuesday in a statement.
"In this day, that is a rare attribute. When he and I spoke at the end of the season, we agreed that if an opportunity presented itself in which his chance to play would be enhanced, we would pursue it, and that's what we've done.
"He deserved the chance to play more."
The 32-year-old lefthand-hitting Pierre is owed $18.5 million on his contract for the next two seasons. ESPN.com reported that the Dodgers will pay $3 million of that salary for next season, and an additional $5 million in 2011.
Over his 10-year career, the speedy Pierre has a .301 batting average and a .348 on-base percentage. He hit .308 with 30 stolen bases and 57 runs scored with the Dodgers in 2009.
The acquisition of Pierre likely means last year's leadoff hitter for the White Sox, Scott Podsednik, is on the trading block.
(Writing by Steve Ginsburg in Washington; Editing by Justin Palmer)