Iris began writing after her children left home for college. She first achieved success in the early 1980s writing category romances. In 1991, Johansen began writing suspense historical romance novels, starting with the publication of The Wind Dancer. In 1996 Johansen switched genres, turning to crime fiction, with which she has had great success. She has had 17 consecutive New York Times bestsellers.
Johansen lives near Atlanta, Georgia and is married. Her son, Roy Johansen, is an Edgar Award-winning screenwriter and novelist. Her daughter, Tamara, serves as her research assistant.