Imada fired a 6-under-par 66 on the Devlin Course at Quail Hollow Resort in Concord, Ohio to take a three-shot advantage at 20-under-par over Heath Slocum, who shot 69.
Slocum and Imada started the third round tied at the top, but Imada took the outright lead with a birdie at the par-3 6th and never looked back.
Imada recorded eight birdies and two bogeys on Saturday, while Slocum posted but one red number after the fourth hole.
Jim Benepe is in third place at 16-under following a 68.
Full-field scores from the Buy.Com Greater Cleveland Open