Kate, 31, and the 28-year-old British actor, who have had an an on-off relationship for four years, recently decided to break-up for good, reported Us magazine.
"Max and Kate have broken up and gotten back together a few times over the course of their relationship, but this one looks like it's sticking. The relationship just ran its course," a source said.
Kate, who was nominated for Outstanding Guest Actress in a Drama Series at the Emmy Awards in Los Angeles, attended the event without 'The Internship' star.