The news was confirmed to People magazine by her rep on Wednesday.
The couple was recently seen on an outing at Oscar’s Cerveteca in Venice, Calif.
Tamblyn, 28, who is the the daughter of actor Russ Tamblyn from the West Side Story, is known for her role in General Hospital and Joan of Arcadia. In 2005 she starred in the hit movie The Sisterhood of the Traveling Pants. Recently she landed a role on House.
David Cross, 47, is famous for his role in the sitcom Arrested Development. He currently appears in the British-American comedy TV series The Increasingly Poor Decisions of Todd Margaret.