Mike James hit all five 3-pointers he took, scoring 26 points Saturday night as Lamar held off Rice 87-81.
Anthony Miles scored 19 points, going 15-for-18 from the free throw line, and Devon Lamb had 17 points and 11 rebounds as the Cardinals (8-3) won their fourth in a row and seventh of eight.
Arsalan Kazemi had 23 points and 12 rebounds to pace the Owls (7-3), whose four-game winning streak ended.
Tamir Jackson scored 24 points and Connor Frizzelle had 12, becoming the 29th player in Rice history to reach 1,000 points. He has 1,004.
Though outscored 62-50 from the field, Lamar made 37 free throws to 19 for Rice.
With the Cardinals leading 18-17, James fueled a 15-3 run with eight points that put them ahead 33-20 with 6:59 left in the first half.
The Owls pulled within four in the final 2 minutes but got no closer.
