Karen Moncrieff was born on December 20, 1963 in Sacramento, California and raised in Michigan. She attended Northwestern University, as a performance studies major. In 1985, she was crowned Miss Illinois and competed in the Miss America pageant. After college she moved to New York and immediately landed the role of Patricia Murphy on the daytime drama Guiding Light.

In 1987, Karen relocated to Los Angeles and quickly won the role of Gabrielle Pascal on Days of Our Lives. She stayed on Days for two years, then appeared briefly on The Bold and the Beautiful and secured the role of Cassandra Benedict (later Lockridge) on Santa Barbara.

Karen has also guested on several television series, TV movies and feature films. After leaving daytime in 1992, Karen established herself as a screenwriter and director. She wrote and directed the 2006 film The Dead Girl.

Karen has been married to Eric Karten since 1987.