Sonya Walger was born in Hampstead, London. Walger was educated at the independent Wycombe Abbey School and at Christ Church, Oxford, where she studied English Literature, receiving a first class degree. Walger is conversational in French and fluent in Spanish, as her father is Argentine.
　　In 1998, Walger played Becky in one episode of Midsomer Murders. She portrayed Flic in Goodnight Sweetheart in 1999, and appeared in two episodes of the crime/drama The Vice. She played Donna Barnes on the HBO TV series The Mind of the Married Man in 2001. On the US version of Coupling, which aired in 2003, she played Sally Harper.Other acting roles have included guest appearances on Lost as Desmond's girlfriend, Penelope "Penny" Widmore and recurring roles on Sleeper Cell and CSI: NY. In 2004, Walger played Nicole Noone opposite Noah Wyle in The Librarian: Quest for the Spear.
　　In 2007, Walger appeared in the original Broadway production of Frost/Nixon, as Charlotte Cushing, David Frost's then-girlfriend. Then she starred in the controversial HBO series Tell Me You Love Me. The series gained notoriety even before the first episode had aired because of the frequency and extremely realistic nature of its sex scenes. Despite persistent rumours to the contrary, these scenes were eventually confirmed as simulated by several individuals intimately connected with the show. With reference to the manual masturbation apparently performed by Walger on actor Adam Scott at the end of the pilot episode,[3] show creator Cynthia Mort stated that "Sonya is not going to put her hands in a place that they shouldn't be."[4][dead link] Director Patricia Rozema and Walger's co-stars Ally Walker and Jane Alexander also explicitly denied that any actual sex took place on set.