Delgado made 7 of 12 shots and grabbed seven offensive rebounds.
Seton Hall led 34-26 at halftime and opened the second half on a 25-9 spurt through eight minutes. Delgado made five baskets during the second-half run and Khadeen Carrington hit two 3-pointers.
Isaiah Whitehead had 19 points and seven rebounds for Seton Hall (14-6, 4-4 Big East), which had lost four of its last five - three to ranked opponents. Carrington finished with 11 points.
Christian Jones scored 15 points for St. John's (7-14, 0-8), which has lost 11 games in a row. St. John's was held to 21-of-72 shooting (29 percent) and got outrebounded 56-40.