Bledel's publicist, Meghan Prophet, confirms the news, which was first reported by Us Weekly. She says the couple have been dating for about a year.
The 33-year-old Kartheiser plays ad man Pete Campbell on the hit AMC network drama, where, last season, Pete had an extramarital affair with the wife of a commuting friend. She was played by Bledel in a guest-starring role.
The 31-year-old Bledel is best known for her role as the teenage daughter in the long-running series "Gilmore Girls," and for her performances in "The Sisterhood of the Traveling Pants" and that hit movie's sequel.
