Flemings' basket with 3:43 remaining in overtime made it 56-55 and gave the Rainbow Warriors (1-2) the lead for good. The Bengals (1-1) pulled to 60-59 on Amorrow Morgan's two free throws with 1:09 left, but Kareem Nitoto and Amis each made two free throws for Hawaii to make it 64-59 with 7.5 seconds left.
After both teams traded free throws, Morgan hit a 3-pointer to cut the lead to 66-64 with 1 second left. But Adhar Mayen made a free throw for Hawaii and Amis intercepted Idaho State's inbound pass as time expired.
Morgan led Idaho State with 26 points and Demetrius Monroe added 14.
The game was part of ESPN's College Hoops Tip-off Marathon and started at 11 p.m. local time.