Publicist Jeffrey Lane said Frann died in her sleep, but he did not know the cause of her death.
Frann spent eight years (1982-90) playing Joanna Louden on the CBS series Newhart. For the most part, her role was to play "straight man" to Newhart's dry-witted, often befuddled, character.
A former child model who studied drama at Northwestern University, Frann broke into television as a weather reporter at a local station in St. Louis. Later, she moved to Chicago, where she worked for four years as co-host of a local morning show.
She first appeared as a regular on the TV series Return to Peyton Place (1972-74).
Frann moved to daytime TV in 1974, playing Amanda Peters for five years on Days of Our Lives. Just before joining the cast of Newhart, Frann appeared in the short-lived TV series King's Crossing.
Her other TV work included the miniseries Jackie Collins' Lucky/Chances and TV movies including Eight Is Enough: A Family Reunion and The Hitchhiker. On stage, she appeared in Story Theater and Love Letters.
The actress was active in charities. The night before she died, she was working with homeless women at the Los Angeles Mission, where she served on a celebrity volunteer committee.
Frann is survived by two sisters and a brother.