The Owls opened the second half on a 10-run and led 31-30. Southern Miss answered with a 10-3 spurt to retake the lead, 40-33. Jackson Trapp scored five points and Solomon Poole added three to pull Florida Atlantic to 42-41.
Quinton Campbell split a pair of free throws and Southern Miss had its last lead, 43-41 with 6:11 remaining. Poole made a pair of free throws, sparking a 13-4 spurt and the Owls led 54-47 with 46 seconds left. Delph scored five points, Jeantal Cylla and Nick Rutherford chipped in three points apiece during the stretch.
Trapp scored 15 points to lead Florida Atlantic (3-14, 1-3 Conference USA). Poole finished with 11.
Tim Rowe had 20 points for Southern Miss (4-11, 1-3).