The club was looking to trim the number of pitchers in camp, because starters are now going deeper into games and there are fewer innings to go around.
The latest move leaves the Blue Jays with 29 pitchers attending Major League Spring Training, with more cuts expected next week.
Mills was the only pitcher who had experience in the Majors. Over the past two seasons in Toronto, he is 1-1 with a 7.80 ERA in 30 innings. He likely will become a candidate to receive a callup if the Blue Jays' staff suffers a number of injuries during the year.
Toronto now has a total of 54 players left in camp, including 18 non-roster invitees.