Julie Sommars was born in Fremont, Nebraska to a government grain inspector and schoolteacher. She attended schools in Iowa, Nebraska, and South Dakota. While a student in Onawa, Iowa, her father, without her knowledge, entered her name in a worldwide talent hunt. Fifteen-year-old Julie found herself in Chicago auditioning for Otto Preminger for the lead role in his film "Saint Joan." She didn't get that part, but as a high school senior she did win the American Legion State Oratory Contest in Aberdeen, South Dakota. She was the only female winner in all of, what was then, the 48 states.

After graduation from high school, Julie took the Greyhound bus to California for a summer job teaching horseback riding and swimming, and attended San Bernardino Valley College. Her appearance in the play, "Our Town" led to her playing Loretta Young's daughter in an episode of the "Loretta Young Show." She was 19.

Her big break came in another talent hunt. She competed for and won the female lead in Ross Hunter's talent hunt for unknowns to play in his 1966 black comedy, "The Pad and How to Use It," based on the Peter Shaffer play, "The Private Ear."

In 1969 she starred in the comedy series, "The Governor and J.J." playing Dan Dailey's daughter, J. J. In 1970 she won a Golden Globe for Best Actress in a Musical or Comedy, tying with Carol Burnett, as well as the Best New Star Award from the Television Critics Association for her role as J. J.

Julie also starred with Dean Jones and Don Knotts in the Disney movie "Herbie Goes to Monte Carlo." Episodic television work includes roles in "Get Smart," "Barnaby Jones," "Harry O," "The Rockford Files," "McMillan and Wife," "McCloud," and "Magnum P.I." In the 1970s Julie starred in many movies for television, including "The Harness," "Five Desperate Women," "Cave-In," and "Centennial."

From 1987-1994 Julie joined Andy Griffith in "Matlock," playing his love interest Assistant District Attorney, Julie March. In 1990 she received her second Golden Globe nomination for Best Supporting Actress in a Drama for the role.

Upon retiring, from March 1999 to March 2000, she served as a public member on the California Judicial Performance Commission. From 2000 to 2003, she served as a public member on The Board of Governors for the State of California.

In 2021 Julie lives in California with John Karns, her husband of 38 years. Between them they have three children, Jacey Erwin, Mike Karns, and Bill Karns.