Born in Manhattan, Michaelsen followed her parents into show Business. Her father, Arne Markussen, is a singer. Her mother, Roberta Stevenson, was a Dancer. She sang on the Soundtrack for Sesame Street and was performing in Off-Broadway plays by age 11. In 1975 her family moved to Beverly Hills and Michaelsen (who changed her name from Markussen) soon won guest spots on such shows as Diff'rent Strokes and Eight Is Enough. Her father is of Norwegian heritage.
She graduated from Beverly Hills High School in 1979 and studied at University of California, Los Angeles. She retired from television work in 2001. Kari has been doing public speaking and hosting educational seminars since 1990. She married David Waldock, a Mercedes-Benz executive, in July 2002. The couple had a son named Nickolas. Michaelsen and David Waldock were divorced in 2009.
