The actor will reprise his role in the upcoming American Reunion, which will see the majority of the original castmembers reunited.
"He hasn't changed at all," he told E!. "That's him. We all know that guy. They haven't changed at all. In fact, they've probably gotten worse."
He added that it felt strange to be playing the role again after so many years, saying: "Yeah, it's really gross. The fact that I'm 34 and these guys are 18. I'm like, 'Holy s**t, I'm way older than these guys'."
American Reunion will focus on the original characters attending a high school reunion, with main characters Jim (Jason Biggs) and Michelle (Alyson Hannigan) now having a child named Owen Dimbylow.
Most of the original cast have signed on for the sequel, including Chris Klein, Eddie Kaye Thomas, Thomas Ian Nicholas, Tara Reid, Mena Suvari, Shannon Elizabeth, John Cho, Jennifer Coolidge, Natasha Lyonne and Eugene Levy.
Seann William Scott was recently said to be coping well after completing a stint in rehab earlier this year.
Watch a compilation of Seann William Scott as Steve Stifler below (contains very strong language):