Senior captain Emma Morgan led the Lady Cardinals' offense with 12 points.
"It's an awesome feeling because we have worked tremendously hard this season and being able to have our work pay off in the end was awesome," Morgan said. "It's been an awesome season."
The Lady Cardinals (20-9) claimed their first state championship since 1999 and third overall.
"We've gotten better every game," said St. Paul coach Dana Beal-Sestak. "We try not to pay attention to the standings of teams because we want to focus on every game and every practice to get better."
The Lady Cardinals took a 21-11 lead at halftime. The Lady Tigers outscored St. Paul 13-8 in the third quarter to trail 27-24 to start the fourth.
"The third quarter was huge for us," Morgan said. "They came back and were ready to bring it and we knew they were going to come out strong, but we were ready and prepared."
"We missed a few shots and had poor defensive plays," Beal-Sestak said. "But we refocused and got back to playing our defense."
The Lady Cardinals regrouped by outscoring the Lady Tigers 11-7 in the fourth to reclaim their lead.
"It was a team effort," Morgan said. "All year long, we've done a great job for players to step up when someone is having a tough day, and it's made us a lot stronger."
Delynn Pesek, Christine Wagner and Gracey Novosad combined for 19 points in the win.
"When we got done, I told my teammates I am so very thankful for each and every one of them," Morgan said. "We wouldn't have won this game without one person being here and without their hard work and dedication."
TAPPS Class 2A State Basketball Championship Shiner St. Paul 38, Muenster Sacred Heart 31 Points - (St. Paul) Riley Johnson 3, Delynn Pesek 8, Gracey Novosad 5, Parker Clay 4, Christine Wagner 6, Emma Morgan 12. 3-pointers - Riley Johnson 1. Halftime - St. Paul 21, Muenster Sacred Heart 11. Records - St. Paul 20-9, Muenster 31-6.