Karina's rep tells E!'s Marc Malkin, "I am confirming that they did indeed break up."
After dating for six months, Maksim had popped the question in Las Vegas on New Year's Eve 2009.
Maks and Karina will both compete this season on "Dancing" -- Maksim is paired with "Entourage" star Debi Mazar and Karina is partnered with former pop star Aaron Carter.
Season nine of "Dancing with Stars" premieres September 21 on ABC.