The win moves the Ragin' Cajuns (6-9, 2-2) into a tie for first place with the Trojans (8-7, 2-2) in the Sun Belt's West division.
Mbamalu was 9-of-14 shooting and also had four assists. Shawn Long added 10 points and 13 rebounds for his eighth double-double this year and third in four games.
Louisiana shot the ball well offensively in the game, going 27-for-55 from the field (.491) and 18-for-25 from the line (.720) with seven three-pointers to help offset being out-rebounded 44-32, including 21-7 on the offensive glass. UL turned the ball over a season-low nine times.
The Cajun defense forced just 10 turnovers but did apply enough pressure to limit UALR to .313 shooting (21-67), the lowest effort by a Cajun opponent this year.
Will Neighbour turned in 17 points and a career-high 14 rebounds for his third double-double of the season. The junior hit 9 of 11 free throws and the Trojans made 24 of 30 while connecting on 31.3 percent (21 of 67) from the floor.
Louisiana trailed 37-34 at halftime but came out of the intermission with a 7-2 run.
The lead would change hands several times in the next couple of minutes before Mbamalu would score five straight points, including a three-pointer with 13:22 left that made it a 49-45 game.
The Trojans would come no closer than five points after that.
The Cajuns will open a two-game swing through Florida by playing at Florida Atlantic on Thursday, Jan 3 at 6:00 p.m. CST and at FIU on Saturday (Jan. 5) at 6:30 p.m. CST.