SLU's 2-1 win on Saturday night before 3,864 fans gave it a share of the tournament title with Creighton, which had beaten Indiana by the same score on Thursday.
Indiana went ahead on a goal by midfielder Brad Ring from 20 yards, but it couldn't hold the lead.
Former U.S. U-17 Brian Grazier scored his first career goal on a tap-in in the 42th minute after a ball from Dado Hamzagic squirted out of the hands of goalie Chay Cain.
Kyle Patterson put away the game-winning goal in the 60th minute after an IU miscue in front of the area.
"I am pleased with the overall effort of the team, but costly mistakes hurt us," said Hoosier coach Mike Freitag. "You can't do that against a quality opponent like Saint Louis."
The win was the second straight for SLU, which had opened the season with two ties and a loss.
"To get a win over a top 10 team like Indiana is a great result," SLU coach Dan Donigan. "We made one mistake, and Brad Ring scored a beautiful goal. But I liked how we bounced back and tied the game before halftime on Brian Grazier's goal. Kyle Patterson was overpowering tonight. Indiana had possession, but he took the ball away and scored. I'm very happy and pleased with how we played."
Byron Dacy's overtime goal gave Creighton a 1-0 win over Loyola Marymount in Saturday's first game.
Dacy had played just two minutes this season prior to Saturday because of a torn left ACL he suffered on Aug. 18.
Saint Louis/Nike Classic All-Tournament Team
Josh Aranda, Co-MVP (Saint Louis)
Tim Walters, Co-MVP (CU)
Kyle Patterson (Saint Louis)
Calum Angus (Saint Louis)
Ross Kaufman (Saint Louis)
Seth Sinovic (Creighton)
Chris Schuler (Creighton)
Jeff Thayer (Creighton)
Adam Sloustcher (Loyola Marymount)
Nick Blanco (Loyola Marymount)
Brad Ring (Indiana)
Greg Stevning (Indiana)