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).

[3][4] Her father was a civil engineer, who worked initially as a municipal employee for Kansas City and later as a private contractor.

[5] Her mother, described as "an accomplished mezzo-soprano", taught Betty in her early childhood to sing and enrolled her in the Kansas City Conservatory of Music when she was only five years old.

At age 18 she was part of a USO tour in the China Burma India Theater during World War II.

"[6] Betty Lynn began her acting career in radio as a member of the cast on a daytime drama on a station in Kansas City.

[14] A clause in her contract allowed the studio to drop her at six-month intervals, leading to recurring concerns for Lynn.

[13] That same year, she appeared in June Bride with Bette Davis followed by roles in Mother Is a Freshman (1949), Cheaper by the Dozen (1950), and Payment on Demand (1951).

[16]: 1064  In the 1953–1954 television season, Lynn was cast as June Wallace, the sister-in-law of the Ray Bolger character on the ABC sitcom Where's Raymond?

[2] Despite playing the role for five years (1961–1966), she appeared in only 26 episodes, and was never signed on to the show (in part because at the time she was cast, she was still under contract for Texas John Slaughter).

[15] In 1986 she joined her former Andy Griffith Show castmates for the NBC reunion movie Return to Mayberry, in which Thelma Lou finally married Barney Fife.

[18] By July 2019, she was still residing in Mount Airy and continued to make monthly personal appearances in town at the Andy Griffith Museum, signing autographs and meeting with her fans.