Wesley Sanders had 18 points and nine rebounds for Harvard (2-2), and Laurent Rivard had 15 points.
Jones made 8 of 11 shots from the field and handed out five assists. He scored 18 of his points in the first half as the Hawks (3-1) took control from the opening tip. St. Joseph's never trailed and led 13-3 in the first six minutes on a 3-pointer by Jones, one of four he made for the night.
The Hawks made a 14-4 run, led by two 3-pointers from Jones, and built a 27-9 lead with 8:33 to play and cruised to victory.
St. Joseph's forced 18 turnovers while committing only seven. The Hawks also held Harvard to 38 percent shooting from the field (19 of 50) while shooting 30 of 67.
Maryland point guard Melo Trimble, considered a lock to leave the program before struggling in the second half last season, has withdrawn from the NBA draft and will return for his junior season.
Louisville's Chinanu Onuaku, who recently underwent a medical procedure to correct a heart rhythm issue detected during the combine, will keep his name in the NBA draft pool.
Andrew White III will return to the Nebraska men's basketball team next season after removing his name from the NBA draft.