Marcus Marshall scored 12 for MSU, including 9 in the second half, while Dorrian Williams added 10, and Camyn Boone added 8 points and 8 rebounds.
Southern Illinois (7-7) got 16 points from Anthony Beane and 10 from Jordan Caroline.
After MSU took its biggest lead of the night, 33-17, on a Williams step-back jumper just three minutes into the second half, the Salukis embarked on a 10-1 run over the next three minutes. Back-to-back 3-pointers by Beane and Deion Lavender and got a dunk by Caroline highlighted the outburst and made it a 34-27 game with 14:35 to go.
The Bears got a 3-pointer by Williams to push the lead back to 10 and rode the momentum of a Marshall pull-up jumper at the 12:34 mark to lead 39-29.
But foul trouble soon ensued, and even though SIU went nearly 9 minutes without a field goal, the Salukis made a living at the foul line and made 9-of-12 over a seven-minute span to make it a 44-38 contest with five-and-a-half to go.
SIU’s Sean O’Brien scored on a slashing layup from there to make it a four-point game, but Tyler McCullough stepped up for the visiting squad with a jumper that put MSU ahead 46-40 headed into the final media timeout.
Freshman Deion Lavender came out of the media break with a 3-pointer for Southern to get the home club within three for the first time since the opening five minutes of the game. But the Bears kept their poise and rallied behind a Marshall 3-pointer from the right wing just inside the three-minute mark, and later pushed ahead 53-47 on a Boone put-back with 68 seconds remaining.
SIU got it back to 53-49 on a Beane basket and then made it a 53-50 game with 9.3 seconds left after Caroline made one of two at the line.
The ensuing in-bound pass by the Bears was picked off by Beane whose desperation 3-point attempt in traffic as time expired was off its mark to preserve the Missouri State win.
Missouri State’s defense held SIU to just 12-of-36 (.333) from the field while forcing 15 turnovers and snagging 6 steals. The Salukis were just 4-of-13 (.308) from long distance and connected on 22-of-32 (.688) charity shots with 20 second-half attempts.
For their part, MSU was 19-for-47 (.404) overall and 5-of-16 (.313) from bonus distance while capitalizing on 10-of-14 (.714) rare free throw chances. The Bears out-rebounded SIU 31-27, but their 14 turnovers were their second-most of the young season.
Bears’ head coach Paul Lusk improved to 4-0 in conference openers, while MSU earned its sixth straight win in Valley openers to improve to 16-9 since joining the league in 1990-91.
In the first half, Missouri State forced 14 turnovers and held the Salukis to just 2-of-11 (.182) from the field to take a commanding 26-15 lead into the break.
Southern shot 10-of-12 at the line in the first half to help fill the 12-minute void without a field goal in the early going.
After Missouri State built a 14-5 lead midway through the period on a trey by Williams, SIU whittled its deficit to 16-13 after a 6-0 run led by three charity shots by Bola Olaniyan.
The Bears closed out the half on a 10-2 run in the final three minutes with Marshall banking in a 3-pointer at the buzzer to give the visitors their biggest lead of the night.
The Bears return to Springfield on Saturday afternoon for their league home opener at 3 p.m., against Drake (3-10, 0-1) in a regionally-televised game on FOX Sports Midwest.