Forward Jacob Parker hit a jumper with a minute let in overtime to put the Lumberjacks ahead 76-73 and forward Thomas Walkup added a free throw.
VCU guard JeQuan Lewis had a good look at a tying 3-point in the closing seconds, but it failed to drop.
The No. 5-seeded Rams (26-9) led 65-59 with 56 seconds remaining in regulation after a 3-pointer by guard Jordan Burgess. But the No. 12-seeded Lumberjacks (32-2) failed to wilt in winning their 29th consecutive game.
The Lumberjacks were paced by Parker's 22 points.
Guard Treveon Graham had a team-high 19 points for VCU.
Stephen F. Austin made a late push after falling behind 60-50 with under four minutes to play. When guard Deshaunt Walker sank a 3-pointer, the Lumberjacks trailed by three with two minutes to play.
But Burgess drained a key 3-pointer with under a minute left to push VCU ahead by six. It was not enough.
The game had turned quickly, just as it appeared Stephen F. Austin would run away it.
Instead, it almost got run over.
But a 40-30 edge was lost when VCU blitzed the Lumberjacks with a 20-3 run that featured a seven-minute stretch in which Stephen F. Austin scored but one field goal.
The score was tied at 8 five minutes in and the first half a pretty much a give-and-take affair for the remaining 15 minutes.
Stephen F. Austin took an 18-13 lead midway through the half on three inside baskets by Walkup, Gajic and Parker. But VCU tied it on a 3-pointer by guard Doug Brooks and a putback by forward Juvonte Reddic.
Burgess' 3-pointer gave VCU a 28-26 edge, but Stephen F. Austin closed the first half with a 10-2 run highlighted by Parker's 3-pointer just before the buzzer.
Parker led all scorers with 11 first-half points. Graham and Burgess each had six for the Rams.Copyright © 2015, RedEye