Born Samille Diane Friesen in Tacoma, WA, Cannon got her start as a showroom model in L.A. following two years of study in anthropology at the University of Washington. Thanks to the help of writer/producer Jerry Wald, who came up with her stage name (which was originally Diane Cannon), she landed a contract at MGM and made her feature film debut playing Wiggles, a troubled high school student in This Rebel Breed (1960). She then appeared in The Rise and Fall of Legs Diamond (1960).
After a couple appearances on Broadway and some work on television, Cannon met and fell in love with Cary Grant, who was 33 years her senior. While involved with him, she placed her acting career on hold. The two married in 1965 and she bore him a daughter. Three years later, Grant and Cannon went through a bitter public divorce.
In 1969, Cannon returned to films in the then-controversial sex comedy Bob & Carol & Ted & Alice and won the Best Supporting Actress award from the New York Film Critics. Her role also won her an Oscar nomination.
The 1970s were her most active period as an actress and Cannon appeared frequently in films. In 1978, she earned another Best Supporting Actress nomination for playing a conniving, adulterous wife in Heaven Can Wait. By the early '80s, Cannon sharply curtailed her feature-film career, but did appear in a few television movies and miniseries.
In 1976, Cannon wrote, produced, directed, and even helped edit a 42-minute film sponsored by the American Film Institute. Titled Number One, Cannon designed it to teach children about sexuality and their bodies. It earned an Oscar nomination for best live-action short. Cannon has since directed two more films, including The End of Innocence, which is based on her autobiography.
Cannon returned to acting on a limited basis in the 1990s and continued to appear on television in such outings as Arnold Schwarzenegger's Christmas in Connecticut (1992) and features such as Out to Sea (1997).