A right-handed pitcher, Mills worked in 19 games for the 1927–28 Boston Braves, and later spent five full seasons (1944–48) as a coach for the Detroit Tigers of Major League Baseball.

Mills was the sole member of manager Steve O'Neill's coaching staff for the 1945 world champion Tigers.

Art Mills was 16 years old when he joined the United States Navy during World War I; he was discharged for being underage after service aboard the battleship USS New Mexico (BB-40).

[2] Listed as 5 feet 10 inches (1.78 m) tall and 155 pounds (70 kg), Mills began his professional pitching career in the Class A Eastern League in 1924, and after three seasons at that level, he made the opening day roster of the 1927 Braves, a struggling second-division team in the National League.

He appeared in 15 games, 14 as a relief pitcher, and earned his only MLB decision when he was charged with an 8–7 loss to the Giants on July 3 at the Polo Grounds.