It was the fourth coaching win in as many matches with in-state foes for Seals, a former all-SEC volleyball player at Mississippi State.
Outside hitter Rachel Cooper opened her senior campaign with a match-high 17 kills and nine digs, while junior Orshi Kriegel registered a double-double with 12 kills and 11 digs on a .455 hitting performance.
State got off to a sluggish start, trailing 19-13 in the opening stanza before rallying to tie the game at 26-26 on a kill by Kriegel. State scored the game's final two points to take the opener 32-30.
The Bulldog offense got rolling and hit at a match-best .333 clip in game two. State built up a 24-15 lead and nailed down a 30-23 win on a kill by Cooper.
The deciding third game featured another close battle, with the two teams batting to a 29-29 stalemate before MSU closed out the game and match by scoring the game's final two points.
"We started playing a little more like I thought we would in the second game," said Seals. "We probably had a case of the opening-game jitters, but we found a way to finish the games and get an important first win."
Sophomore middle blocker Erin Seago had four kills and a match-leading four blocks - a career-best three of them solo stops. Freshman middle Nicole Palazzo, one of five newcomers to see action for MSU in the season-opening match, delivered five kills on seven error-free attack attempts.
USM got a team-best eight kills and eight digs from Kaitlyn Deutsch. Amber Bloom Jazzmien Stephens and Ashley Petrinec each had six kills.
The Bulldogs resume action next weekend in Blacksburg, Va., taking on Wisconsin-Milwaukee, Georgetown and host Virginia Tech Sept. 2-3 in the Hokie Fall Invitational.
MSU 3, SOUTHERN MISS 0
USM (0-1) 30 22 29
MSU (1-0) 32 30 31