Marnie McPhail started acting at age 14, playing teenage sleuth Annie Edison in the Canadian television series The Edison Twins. She attended The Etobicoke School of the Arts in Toronto, Ontario, Canada. She currently resides in Los Angeles with her husband, actor Reed Diamond. They were married in County Clare, Ireland on October 8, 2004.
Marnie is the lead singer of the rock band Chuck Valiant and her husband plays guitar.