The 34-year-old suffered a broken nose, a concussion, black eyes, cuts and bruises, according to a statement.
DeGraw posted an update to fans on his Twitter page Tuesday afternoon, saying he didn't remember much and thanking them for their concern. "Hi my friends. Honestly, I don't remember much. I only know I can recover from here. Thank u all for your genuine concern. I love u guys," he tweeted.
The attack happened early Sunday morning in the East Village. A spokesman for DeGraw said he was taken to Bellevue Hospital in an ambulance.
An investigation is ongoing and no arrests have been made.
DeGraw was forced to cancel concerts this week in upstate New York and Massachusetts due to his injuries, and he postponed his appearance on "Live! with Regis & Kelly," which was scheduled for Wednesday.
DeGraw became popular for his songs "I Don't Want to Be" and "Chariot." His new album, "Sweeter," is due out in September.
The Associated Press contributed to this report.