Sexton stood without flinching as two leaders of NYU's student council doused him in the freezing water for the stunt, which is part of a national campaign to raise money and awareness about the illness, also known as Lou Gehrig's disease.
WATCH JOHN SEXTON DO THE ALS ICE BUCKET CHALLENGE IN SLOW MOTION:
Sexton had been challenged to the ice bucket dump by NYU's men's soccer team and the presidents of other universities, but he said the cause struck a chord with him after historian and professor Tony Judt died in 2010 following a two-year battle with ALS.
"Tony was an extraordinary colleague here at NYU — he was one of the world's great historians," Sexton told dozens of students who gathered in Washington Square Park to watch him get soaked.
Student council chairwoman Jules O'Connor, a senior in the College of Arts and Sciences, and vice chairman Michael Hengerer, a junior at Gallatin, dumped the ice on Sexton, who was wearing an NYU T-shirt and a bathing suit.
Sexton took the opportunity to challenge O'Connor and her counterparts at the Abu Dhabi and Shanghai campuses to also complete the challenge, as well as the new dean of NYU Law School, Trevor Morrison.
A spokesman for New York University said Sexton donated $500 to ALS research.