Bergl was born in Milton Keynes, England to an Irish mother and an English architect father. She lacks a British accent because she moved to Chicago with her family when she was a child and attended Glenbrook South High School and Grinnell College, where she was the lead in several school productions. She graduated Phi Beta Kappa in 1997 with a B.A. in English and Theater. She has a brother.

Bergl's big break came with the lead role of Rachel Lang in the 1999 film, The Rage: Carrie 2, the sequel to the 1976 supernatural thriller Carrie. Much of her acting also takes place on television. Bergl has appeared in episodes of the TV shows Gilmore Girls, CSI: Miami, Medium, Law & Order: Criminal Intent, NYPD Blue, and Star Trek: Enterprise. She also appeared in the psychological thriller Chasing Sleep, opposite star Jeff Daniels.