Manager Mike Scioscia made the announcement Saturday.
Rasmus was 3-2 with a 2.57 ERA in 30 games last year, helping the Angels lead the majors with 98 wins. He made six starts after Garrett Richards was injured.
The 27-year-old righty pitched twice this spring, giving up five runs and seven hits in three innings.
Rasmus made his big league debut in 2013 with Atlanta and was traded later that season for pitcher Scott Downs.