With Rougned Odor continuing to struggle this season, the 31-year-old Dietrich could be an option for the club at second base. He'll report to the team's alternate site.
Dietrich spent time with Cincinnatti in spring training before being released on July 20. He was picked up by the Chicago Cubs on July 23 but was granted his release on Saturday.
Dietrich hit a career-high 19 home runs with the Reds in 2019.