Khem Birch added 11 points and 12 rebounds for the Rebels (17-8, 8-4 Mountain West Conference).
Utah State (15-10, 5-8) was led by Jarred Shaw with 20 points and 12 rebounds.
Trailing by two at halftime, UNLV shot 6-for-6 to open the second half and took their largest lead of the game to that point, 43-36, with 16:25 to play. A 3-point shot by USU's Jalen Moore would tie the game at 45, but behind three layups by Roscoe Smith and Dejean-Jones, UNLV stretched the lead to 50-59 with 6:50 left.
Olekaibe hit his third 3-pointer of the game with 3:07 to play to give UNLV a 58-66 lead and the Rebels made four free throws and two breakaway layups in the final minutes to seal the win.