David Ndoumba added 13 points for the Lions (7-6, 1-0 Southland Conference), which played its first home game since Dec. 1. Stephen F. Austin (9-4, 0-1) entered leading the country in scoring defense at 51.3 points.
There were five ties and seven lead changes in the first half before DeShawn Patterson hit two free throws to give the Lions an 18-16 lead with 6:02 remaining. They didn't trail again.
Southeastern Louisiana shot 58.8 percent from the field (10 of 17) in the second half. Fortenberry went 0 for 6 in the first half, but was 4 of 5 in the second.