In 2003, Mota earned a roster spot with the Dodgers after spring training. From May 1 to May 27, he pitched consecutive scoreless innings. On May 23, against the Milwaukee Brewers, he got his first save when he pitched three scoreless innings in a 6–4 victory. Manager Jim Tracy used him to get the save because he wanted to rest closer Éric Gagné. On May 29, Mota struck out six batters in three innings in a 12–5 loss to Colorado. From June 11 through July 17, he threw consecutive scoreless innings. On July 13, he hit his second career home run (against Joe Roa) in a 9–3 victory over Colorado. In August, he had a 2–0 record with a 0.44 ERA in 21 games. Mota finished the season with a 6–3 record and a 1.97 ERA in 76 games, and his 105 innings pitched were the most by a Dodger reliever since 1985, when Tom Niedenfuer threw . His 105 innings pitched led National League (NL) relief pitchers and were just two shy of American League leader Steve Sparks. Mota, Gagné, Tom Martin, and Paul Quantrill were the first relief pitcher teammates to appear in at least 76 games in a season. His opponent batting average of .205 ranked tenth among NL relievers, and left-handers' .181 average against him ranked fourth in the NL.