The Mocs owned an eight-point halftime lead and expanded their advantage to 12 early in the second before the Jayhawks clamped down on defense.
Chattanooga scored just 13 points over the game's final 18 minutes.
McLemore led the way with 25 points and eight rebounds, helping the Jayhawks avoid what would have been the biggest upset of the young college season. Kansas (2-1) was coming off a three-point loss to No. 22 Michigan State on Tuesday.
Elijah Johnson had 18 points for Kansas and Jeff Withey contributed 11 points and 10 rebounds.
Farad Cobb came off the bench to lead Chattanooga (1-1) with 21 points.