Milwaukee (8-2) had four players in double figures, with Steve McWhorter adding 16 and Austin Arians chipping in with 11. Milwaukee shot 45 percent from the floor, including 10 of 27 (37 percent) from beyond the arc.
Northern Iowa built a seven-point halftime lead, and stretched it to nine a minute into the second half.
But Milwaukee scored the next 17 points, including 3-pointers by Tiby and Aaron, to reverse the tide and give Milwaukee a six-point lead at 13:40 of the second.
Northern Iowa cut the lead to five on a pair of Washpun free throws with 1:32 left, but Milwaukee made four straight free throws to secure the victory.