Sandra Oh was born on July 20, 1971 in Ottawa, Ontario, Canada, and is fluent in both English and French. Oh became interested in acting while attending Sir Robert Borden High School in Nepean, Ontario, where she took drama classes, acted in school plays, and was a member of the drama club. After high school, Oh continued to study drama.

Oh is known in Canada for her lead performances in the Canadian movies Double Happiness (for which she won the Genie Award for Best Actress), Long Life, Happiness and Prosperity, and Last Night (which she again won a Best Actress Genie for). Oh also won FIPA d'Or (Best Actress) at the Cannes Film Festival for her role in The Diary of Evelyn Lau.

Oh is most familiar to American audiences by her supporting role as a put-upon assistant in a sports agency in the long-running HBO series Arli$$, her supporting role in the popular 2004 film Sideways, and her current role in the hit ABC medical series Grey's Anatomy, for which she has won both a 2006 Golden Globe (for Best Television Supporting Actress) and 2006 Screen Actors Guild Award (for Outstanding Performance by a Female Actor in a Drama Series).

In theatre, Oh has also starred in the world premieres of Jessica Hagedorn's Dogeaters at the La Jolla Playhouse and Diana Son's Stop Kiss at Joseph Papp's Public Theatre in New York. She was also seen in The Vagina Monologues in New York.