Terms were not disclosed, but sources told ESPN the Minutemen signed McCall to a five-year contract.
UMass reached an agreement with Winthrop head coach Pat Kelsey last week, but Kelsey had a change of heart shortly before a scheduled news conference to officially announce the hire. Kelsey instead returned to Winthrop.
McCall, 35, had been with the Mocs for two seasons, taking over when Will Wade left for VCU. McCall went to the NCAA tournament in his first season at Chattanooga, going 29-6 and winning the Southern Conference title.
The Mocs struggled down the stretch in 2016-17, losing five straight games to end the season with a 19-12 record. In two seasons, though, McCall led Chattanooga to wins over the likes of Georgia, Illinois, Dayton and Tennessee.
Before moving to Chattanooga, McCall was an assistant under Billy Donovan at Florida for four seasons. He started his career as a manager at Florida and spent two seasons as the director of basketball operations for the Gators. McCall was also an assistant coach at Florida Atlantic for three seasons.
McCall replaces Derek Kellogg, who was fired earlier this month after nine years with the Minutemen.