Illinois State held South Carolina to 29.5 percent shooting, and the Redbirds never trailed, beating the Gamecocks 69-65 on Thursday in the first round of the Puerto Rico Tip-Off at Myrtle Beach at the HTC Center in Conway, S.C.
Milik Yarbrough had 18 points, six rebounds and six assists, and Keyshawn Evans added 17 points for the Redbirds (1-1).
South Carolina (2-1) got within 56-55 with 3:08 left in the game, but the Redbirds pushed the lead back to seven with 1:20 to go.
The Redbirds were 5-for-6 from the free-throw line in the final 43 seconds.
Hassani Gravett and Chris Silva scored 10 points each for South Carolina.
The Gamecocks were 9-for-29 from 2-point range and 9-for-32 from beyond the arc.
It was a much-improved defensive effort for an Illinois State team that gave up 53 second-half points in its 98-87 season-opening loss at Florida Gulf Coast.
The Redbirds scored nine straight points to turn a tie game into a 21-12 lead 5:53 before halftime.
Evans made a 3-pointer with one second left to give Illinois State a 32-23 lead at the break.
South Carolina committed 15 first-half fouls and shot just 23.3 percent — including 3 of 14 from 3-point range — in the first half.
Illinois State jumped out to a 10-3 lead as the Gamecocks missed their first eight shots from the floor.
The Puerto Rico Tip-Off was relocated to the campus of Coastal Carolina University after the commonwealth of Puerto Rico was devastated by Hurricane Maria in September.