After a free throw by Mercer's Phillip Leonard cut the Western Carolina lead to 49-48 with 3:55 to play, back-to-back 3s by Brown and James Sinclair pushed the Catamounts lead back to seven with 2:06 left.
Mercer trimmed their deficit back to two in the waning moments, but a pair of Sinclair free throws sealed the deal.
Sinclair and Rhett Harrelson finished with 13 points apiece and combined to shoot 7 of 13 from behind the arc for Western Carolina (13-13, 8-6 Southern Conference). Overall the Catamounts hit 11 of their 17 attempts from downtown.
Jibri Bryan scored 12 points for Mercer (14-12, 9-4)
The game was Western Carolina's first on the road at Mercer since 1999 and just the third all-time.