Cincinnati announced the moves Saturday before the second game of their series against the St. Louis Cardinals.
Arredondo had reconstructive elbow surgery in February 2010. The Reds signed the 27-year-old to a contract that month and kept him on the disabled list at Louisville last season.
Arredondo went 10-2 with a 1.62 ERA as a rookie with the Angels in 2008. He began to have elbow problems the next season.
Leake opened the season in the rotation, which was gutted by injuries. He moved to long relief when Homer Bailey and Johnny Cueto came off the disabled list. He was 3-2 with a 5.70 ERA in six starts and three relief appearances.