Efejuku fueled a 19-2 run over nine minutes starting late in the first half as the Friars erased an seven-point deficit. Herbert Hill added 16 points and 11 rebounds for Providence.
A dunk by Geoff McDermott gave Providence (16-9, 6-6 Big East) its biggest lead, 42-32, with 13:48 left.
The Red Storm closed to within three, 64-61, on an Anthony Mason 3-pointer with 50 seconds to play. Providence then hit seven foul shots to clinch the game.
Lamont Hamilton led St. John's (15-12, 6-8) with 20 points, including 14 points in the second half and 10-of-10 foul shooting overall.
Mason scored 19 points, including 14 on 6-of-9 shooting in the first half to spark the Red Storm to a 30-28 halftime lead.