The couple were married for six years, reported People magazine.
"After six years of marriage, and having been separated for the past year, Katharine McPhee has filed for a dissolution of marriage from Nick Cokas. The two have an amicable relationship and will remain friends. They ask that people respect their privacy during this time," a representative for the actress said.
Last year, McPhee was photographed kissing her 'Smash' director Michael Morris, who is wed to actress Mary McCormack. Morris has since reconciled with McCormack.