The Hilltoppers (16-8, 9-3) fall a full game behind Conference USA leader Louisiana Tech with the loss.
Western Kentucky led 69-67 on Chris Harrison-Docks 3-pointer with 8:03 to go. Marshall (9-16, 5-7) responded by scoring 14 of the next 19 points, including Austin Loop's 3-pointer and a pair from the line by Ryan Taylor, which made it 83-74 with 1:02 left. Western Kentucky missed three consecutive 3-pointers in the last minute.
Loop's 3-pointer with 31 seconds left in the first helped Marshall lead 47-43 at the break.