Mills signed a minor-league contract Thursday with the Reds, Charlie Goldsmith of The Cincinnati Enquirer reports.
The organization's MLB-ready pitching depth has been ravaged by injuries, so Mills will get a look with an assignment first to Triple-A Louisville. He failed to attract much interest over the winter after struggling to a 9.68 ERA in 17.2 major-league innings (two starts, five relief appearances) last season with the Cubs.