At the age of 19, Tunney moved to Los Angeles, California and obtained several recurring TV roles on Class of '96, Law & Order, Dream On, and Life Goes On. She gave her breakthrough performance as a suicidal teenager in Empire Records and attracted further attention by playing a witch in The Craft.In 1997, Tunney starred in Bob Gosse's Niagara, Niagara with Henry Thomas in a performance which garnered her the Best Actress award Volpi Cup at the 1997 Venice International Film Festival. Tunney also was featured opposite Arnold Schwarzenegger in the 1999 supernatural action film End of Days.She starred in the pilot episode of House as a kindergarten teacher who collapses before her class and descends into aphasia; she was credited as a "special guest star". She portrayed Veronica Donovan on the first season of Prison Break, credited third after two main characters. She also appeared in the premiere episode of the second season, and in this episode, her character was killed off. She had a minor role in the film August released on July 11, 2008. Tunney is currently starring opposite Simon Baker in the CBS drama series The Mentalist.Tunney married producer/director Bob Gosse on October 4, 1997; they divorced in 2006. In 2009, Tunney was engaged to Australian writer/director Andrew Dominik but their relationship ended by August 2010. She got engaged to interior designer Nicky Marmet on December 25, 2012 while on vacation in Rio de Janeiro.On June 28, 2006, Tunney won the fifth table of Bravo's Celebrity Poker Showdown's eighth season, finishing ahead of Christopher Meloni, Macy Gray, Joy Behar, and Andy Dick, moving on to the final cut. The finale aired on July 5, 2006, where she competed against Jason Alexander, Michael Ian Black, Ida Siconolfi, and Keegan-Michael Key. Tunney came in second, behind Alexander. She played for The Children's Health Fund, which received $200,000 for her efforts. In August 2006, Tunney played in the World Series of Poker after having her entrance fee covered by the online cardroom PokerRoom.com.