The 23-year-old Hilton hotel heiress/reality TV star, and Carter, of the Backstreet Boys, had dated for seven months.
It was Hilton who ended the romantic relationship, said her publicist, Gina Hoffman.
"She's concentrating on her work," Hoffman told the AP.
Carter, 24, told People magazine Friday that he feels good, despite the break up.
"This is the time of my life," he said. "I'm back in the studio ready to go on tour with the guys."
He added: "I want to be free to date other people and I got tired of all the rumors" of trouble in their relationship.
A new Backstreet Boys (search) album is expected to be released later this year.
Hilton will begin shooting in August for her first starring film role in "Pledge This," about a college sorority. She's starred for two seasons on Fox's "The Simple Life" (search) with her friend Nicole Richie (search).