A 9th-inning home run by freshman Daniel Pacella tied the game but SIUE ultimately won, 6-5, in 10 innings as a two-out ground ball went under the glove of a Redbird infielder, plating the runner from second base.
SIUE scored twice in the 1st inning before senior Dylan Swarmer knocked in junior Adrian Flores in the 3rd inning.
In the 6th inning, junior Luke Cheng singled home junior Auggie Rasmussen prior to two more Redbirds scoring on RBI outs, yielding a 4-2 ISU lead.
The Cougars responded with three runs in the 7th inning to retake the lead.
Pacella's home run to left-center to tie the game in the 9th inning was the first of his career but SIUE walked it off in the 10th inning.
Freshman Thomas Harper made his first career start, settling in with three-straight scoreless innings after conceding two runs in the 1st inning.
The Redbirds fall to 2-2 and the Cougars improve to 3-1.
Illinois State is scheduled to play Friday-Sunday at Arkansas State.