Two 3-pointers by Carl Jones started an 18-5 run for the Hawks (13-7, 4-3 Atlantic 10 Conference), who trailed their local rival 61-52 with 5:39 left.
C.J. Aiken put Saint Joseph's ahead 68-66 with a layup off a lob from Halil Kanacevic at the 25-second mark.
After two free throws by Kanacevic, Khalif Wyatt's 3-pointer for the Owls (14-7, 3-4) made it a one-point game. Wyatt finished with a career-best 34 points and made 7 of 14 3-pointers.
Jones missed a free throw, but Wyatt had the ball go off Saint Joseph's on a drive, then couldn't hit a final shot with time running out.
Jones and Aiken scored 16 points each for Saint Joseph's. Kanacevic had 12 points, nine rebounds and eight assists.