The Bearkats (18-6, 10-2 Southland Conference) led by 16 early in the second half as Jabari Peters hit two 3-pointers.
Northwestern State (11-12, 7-5) surged back late as a Patrick Robinson steal led to three Jalan West free throws with 3 seconds left. Paul Baxter split a pair of free throws, and Zikiteran Woodley's 40-foot heave at the buzzer couldn't find the net.
SHSU shot just 35 percent from the field, but outrebounded Northwestern State 49-39. The win for the Bearkats sets up a showdown with Southland-leading Stephen F. Austin on Saturday.
The Demons shot 35.9 percent and were 3 of 16 beyond the arc. West finished with 12 points, 10 rebounds and nine assists. Brison White added 19 points and DeQuan Hicks had 16.