Dunham finished with a game-high 29 points and tied Butler's single game record for 3-point shooting accuracy by hitting seven of seven long-range attempts. He matched the mark set by Avery Sheets against Loyola on Feb. 3, 2005.
Dunham finished the game hitting 11 of 14 shots.
"(Kellen's) had some good shooting performances, but I haven't seen him make the shots consecutively that he did to start tonight," Bulldog coach Brandon Miller said in a release. "You felt like every time the ball left his hand it was going to go in. He got some good looks, but he also made some tough shots."
Dunham scored the first five points of the game, and Seton Hall (15-16, 6-12 BE) never caught up.
The Bulldogs led 15-4, less than five minutes into the game and stretched that margin to as many as 20 points, before settling for a 40-30 halftime lead.
Dunham finished the first half with 19 points, hitting all five of his three-point attempts.
As a team, Butler (14-16, 4-14) shot 53.8 percent (14-26) in the opening half, including 61.5 percent (8-13) from beyond the 3-point arc.
"I'm extremely proud of our guys' effort," Miller said. "I thought our mind-set and our approach from the very start was exactly where it needed to be.
"We came out with an energy about us. It always helps when you go eight for eight from 3-point range to start the game, but along with making shots, we defended."
The Bulldogs opened the second half with a 17-7 run to stretch the lead back to 20 points and Seton Hall never got closer than 14 the rest of the game.
The game was the final regular season contest at Hinkle Fieldhouse for seniors Khyle Marshall and Erik Fromm and both were honored prior to the game. Marshall finished with 10 points and six rebounds, while Fromm added nine points and three rebounds. It was the 91st career win for the two Butler seniors.
"I don't know if it's really hit me yet that I won't get to play in Hinkle again," Fromm said. "As always, the fans were great. It's always a special night. You come through the program and see the seniors graduate, and you never think it's going to be your turn. And then it finally is and you really don't know how to feel about it.
"I can tell you this, I would not want to spend 'Senior Night' anywhere else but Butler."
Marshall echoed Fromm's thoughts.
"That was a very magical moment," Marshall said. "All the fans and our teammates there to share this with us and our families."
In addition to the contributions from Dunham and the seniors, Butler picked up 10 points from freshman Elijah Brown in a reserve role.
Junior Alex Barlow, coming off a career-high 19 points in Butler's win at DePaul two nights earlier, chipped in with nine points, eight rebounds, four assists and three steals.
Junior Kameron Woods, the leading rebounder in the conference, topped both teams with nine rebounds.
Patrik Auda came off the bench to lead Seton Hall with 22 points, while Sterling Gibbs added 11. Center Eugene Teague finished with 10 points and a team-high six rebounds.
Butler will enter the Big East Tournament at Madison Square Garden as the No. 9 seed, while Seton Hall finishes as the No. 8 seed.