On January 14, 2009, the Los Angeles Dodgers announced that they had signed free agent Guillermo Mota. The deal marks a return for Mota, who played for the Dodgers in 2002, 2003 and 2004.MLB.com: As Mota arrives, Jones on the way out (January 14, 2009)

On December 9, 1996, Mota was drafted out of the minors by the former Montreal Expos. Mota was called up three years later to make his MLB debut with the Expos on May 2, 1999. He played 51 games in 1999 with the Expos, ending the season with a 2.93 earned runs average. He continued with the Expos for the next two seasons, playing 29 games in 2000 and 53 games in 2001.

Mota was traded shortly before the start of the season to the Los Angeles Dodgers on March 23, 2002. He stayed with the Dodgers for the next two and a half seasons, averaging around 75 games each season.

On July 30, 2004, Mota was traded to the Florida Marlins, where he finished the 2004 regular season. On November 24, 2005, Mota was traded to the Boston Red Sox. He did not play a single game with the Red Sox, as they sent him to the Cleveland Indians just two months later on January 27, 2006.

Mota played 34 games with the Indians in 2006, before he was traded again, this time to the New York Mets on August 20, 2006. Mota made his first post season appearance with the Mets in 2006, where the Mets lost the National League Championship Series to the St. Louis Cardinals.

Following the 2007 season, the Mets traded Mota to the Milwaukee Brewers on November 20, 2007.