The Dodgers announced Wednesday they hired McGwire to be their hitting coach.
"Being away from my family a lot this year was really, really rough," McGwire said. "I was very surprised when I found out the Dodgers called last week."
McGwire, who broke baseball's single-season home run record in 1998 and later admitted to using steroids, lives in Orange County, about 40 miles south of Dodger Stadium.
McGwire informed the St. Louis Cardinals he was accepting the Dodgers' offer last week. The Cardinals on Friday promoted John Mabry to be McGwire's successor. The Dodgers also will announce in the coming days that they have hired an assistant hitting coach, general manager Ned Colletti said.
"As we played St. Louis the last few years and I talked to our staff, the conversation was always about how well they adjusted inside the game and adjusted inside at-bats, how they prepared," Colletti said. "We saw how our pitchers struggled at times against St. Louis because their preparation was so strong."
The Dodgers fired Dave Hansen as their hitting coach shortly after the season ended.
McGwire, a 12-time All-Star, came out of seclusion to serve as former Cardinals manager Tony La Russa's hitting coach in 2010 and stayed in St. Louis under Mike Matheny last season.
The Dodgers have been through four hitting coaches since 2008, a group that includes their manager, Don Mattingly.
In McGwire's three seasons in St. Louis, the Cardinals have led the NL in batting average (.269) and on-base percentage (.337) and have ranked second in runs (2,263) and fourth in slugging percentage (.416).
The Dodgers finished 13th in the NL in both runs and OPS last year.
McGwire, who grew up in Pomona, just east of Los Angeles, played collegiate baseball at USC, where he set a school record with 32 home runs in 1984.
McGwire retired after the 2001 season with 583 career home runs, fifth at the time on the all-time list, but has not been viewed kindly by Hall of Fame voters, largely because of his link to steroids. In his fifth year on the ballot last winter, McGwire received just 19.8 percent of the votes, well short of the 75 percent needed for enshrinement.
"It's something I did that I have to live with the rest of my life," McGwire said. "It's something where I understand everything the Hall of Fame is all about. I respect that. It's a mistake I've made and owned up to and moved on. I don't know what else to say."
Colletti said it was crucial that McGwire owned up to his steroid use before returning to the game.
"I think we all make mistakes and do things we look back on and, if we had thought twice, we wouldn't have done," Colletti said.