Lynn appeared in 26 episodes of The Andy Griffith Show over a span of five years from 1961 to 1966.
Before that Lynn enjoyed a Broadway career, and was discovered by Daryl F. Zanuck in one of several plays. During the 1940s and 1950s, she appeared in many films, including Sitting Pretty (1948), June Bride (1948) the original Cheaper by the Dozen (1950) and Meet Me In Las Vegas (1956).
She then segued to television, appearing on the Schlitz Playhouse of Stars, The Gale Storm Show, Sugarfoot and Markham.
In 1986, she reprised the role of Thelma Lou in the reunion television movie Return to Mayberry, in which