Western Carolina tied the game at 54-54 with 5:53 left. Illinois guard D.J. Richardson hit 3-pointers on back-to-back possessions for a 62-56 lead. Richardson finished with 13 points.
After a Western Carolina turnover, Illini guard Tracy Abrams made two free throws and a basket on the following possession for a 66-56 lead. Abrams added 10 points for the Illini, who shot 40 percent for the game.
The Illini (9-0) play at No. 10 Gonzaga on Saturday.
Illinois was 3 of 14 from the field to start the game, but the Illini stretched the lead to 32-22 at halftime with a 15-8 run to end the half.
The Catamounts kept the game close despite 22 turnovers. The game served as a reunion for Western Carolina coach Larry Hunter and Illini assistant Dustin Ford, who played for Hunter at Ohio and coached under him at Western Carolina.
Ford worked at Western Carolina for three seasons, concluding in 2008. He then returned to Ohio, where he joined Jim Groce's staff before moving with Groce to Illinois prior to this season. Western Carolina fell to 1-14 all-time against teams from the Big Ten Conference.