The Peacocks became the 10th No. 15 seed to win a first-round game since the tournament expanded to 64 teams in 1985 and handed Kentucky its first opening-round loss under coach John Calipari.
Banks’ two free throws with 1:45 left in overtime gave Saint Peter's the lead for good. Doug Edert’s layup with 24 seconds left in regulation sent the game to overtime. He also made the final two game-sealing free throws for the Peacocks and finished with 20 points.
Player of the year Oscar Tshibwe led the Wildcats with 30 points and 16 rebounds.