Tigers general manager Al Avila said Mize is scheduled to start Wednesday night at Chicago after left-hander Tarik Skubal goes Tuesday night against the White Sox. Mize, 23, was the No. 1 pick overall in the 2018 amateur draft.
Avila said Monday that infielder Isaac Paredes also was called up and infielder Dawel Lugo was designated for assignment.
The rebuilding Tigers have been patiently developing their young players, but a combination of their talent and the team's needs led to the moves.
"We felt they were ready," Avila said.
Mize and Skubal have not pitched above Double-A.
The time was right for Mize at least in part because right-hander Ivan Nova went on the injured list Saturday with triceps tendinitis.
Avila has resisted the temptation to put Mize on the mound in the majors, including earlier this summer, when the pandemic-shortened season started.
The Tigers had Mize and other top prospects in camp at Comerica Park but reassigned them to their alternate training location. The reports from Toledo, Ohio, were positive about how they fared in intrasquad games from people within the organization, including Hall of Fame player and former manager Alan Trammell and ex-manager Jim Leyland.
"It was more important for us that these guys got more work before we rushed them in there," Avila said. "They got close to a month of work."
Mize started 26 games in the minors and went 8-4 with a 2.71 ERA, along with 120 strikeouts over 123 innings.
He was 10-5 with a 2.95 ERA and 151 strikeouts with just 12 walks while helping Auburn's run in the 2018 NCAA tournament. He became the seventh player to go from undrafted in high school to the No. 1 pick, and the first since Stephen Strasburg was taken by the Washington Nationals in 2009.