Forward Kadeem Batts added 15 and eight rebounds as the Friars (17-9, 7-6 in the Big East) hit 10 of their first 11 shots and used a 16-0 run over a 3:55 span to break things open early.
The Friars, who placed a season-high six players in double figures, won for the first time since beating DePaul on the road on Feb. 1.
The loss was the eighth in a row for the Blue Demons, two of those losses to Providence and the last six defeats coming after losing leading scorer and rebounder Cleveland Melvin.
Melvin was suspended for four games because of a violation of team rules, but has left school and the team.
DePaul, which used a 12-2 second-half run to make things respectable, fell to 10-16, 2-11 in the Big East.
Forward LaDonatae Henton added 13 points and six rebounds, forward Carson Desrochers came off the bench with 12 points and five boards, and guard Josh Fortune and forward Tyler Harris each scored 10 points for the Friars.
Cotton, who entered the game second in the Big East in scoring and first in assists, scored only one point over the final 9:55. He came up just short of his 11th straight 40-minute game.
The Blue Demons led, 4-3, two minutes into the game, but the Friars then got hot and blew it open early. By the time the smoke of the first outburst cleared, Providence led, 19-4, six minutes into the game.
DePaul used a 6-0 run to cut what became a 16-point deficit, but the Friars answered and grew the lead to 23 points with 3:56 left in the first half.
Marcius, averaging only 4.8 points per game, had 10 of his team's 26 points in the first half.
NOTES: F Cleveland Melvin, no longer with DePaul after leaving school following a four-game suspension for violation of team rules, was eighth in the Big East in scoring (16.7 points per game) and seventh in rebounding (6.4) entering play on Saturday. ... Providence hosts No. 6 Villanova on Tuesday night, while DePaul is at Xavier Wednesday night. ... Providence G Bryce Cotton had 28 points and six assists in the first game between the teams Feb. 1. G R.J. Curington leading the Blue Demons with 22 points off the bench in that game. ... Providence won on Alumni Weekend.