McMillan was fired in August after four seasons as the bench boss in Indiana. He compiled a solid 183-136 regular-season record, but the Pacers suffered four consecutive first-round playoff exits - including three sweeps - under his watch.
Before joining the Pacers, McMillan served as head coach of the Seattle SuperSonics and Portland Trail Blazers. The 56-year-old's defense-first approach would help a Hawks squad that finished 28th in defensive efficiency last season.
McMillan is also reportedly drawing interest from the Houston Rockets for a spot on new head coach Stephen Silas' staff.