Before becoming well-known for her voice role as Marge Simpson on the animated television series The Simpsons, Kavner attracted notice for her role as Brenda Morgenstern, the younger sister of Valerie Harper's title character in the sitcom Rhoda, for which she won a Primetime Emmy Award for Outstanding Supporting Actress in a Comedy Series.

Known for her improvisation and distinctive "honeyed gravel voice",[2] Kavner was cast in her first professional acting role as Brenda Morgenstern in Rhoda in 1974.

Typically cast as a "woman who is supportive, sympathetic or self-effacingly funny",[2] Kavner grew to dislike playing such roles.

Kavner has also appeared in live-action roles in six films written by Woody Allen and in the Adam Sandler comedy Click.

[6][2] John Ingle, formerly the chairman of the Beverly Hills High School art department, later commented that Kavner was "excellent at improvisation, but she wasn't an ingenue [sic] and not that castable at that age".

She received four Primetime Emmy Award nominations for Outstanding Continuing Performance by a Supporting Actress in a Comedy Series for playing Brenda, winning in 1978.

[3] Series creator Matt Groening instructed Kavner to voice the duo as characters who "suck the life out of everything".

[19] While cast members and crew have referenced Kavner as a deep fan of the series and the characters she voices, part of Kavner's contract says that she will never have to promote The Simpsons on video nor has she performed Marge's voice in public because she believes the publicity "destroys the illusion.

"[20] Nancy Cartwright, who voices Bart Simpson, said in her book My Life as a 10-Year-Old Boy (2000) that Kavner is a warm person who is "a workhorse of an actor" with "extraordinary professionalism and quiet work ethic", and notes that she is rarely late for recording sessions.

[8] In 2004, Kavner and Dan Castellaneta won a Young Artist Award for Most Popular Mom & Dad in a TV Series.

[31] Some scenes in the movie, such as Marge's emotional video message to Homer, were recorded over 100 times, leaving Kavner exhausted.

[32] Many of Kavner's roles have been described by New York Times writer Hilary de Vries as a "woman who is supportive, sympathetic, or self-effacingly funny".

[2] Kavner grew to despise playing such roles, saying "If it smacks of Brenda Morgenstern, I won't take the job.

"[2] She had a supporting role as Eleanor Costello, a nurse who befriends Robin Williams' character in the Academy Award nominated film Awakenings (1990).

Kavner played Dottie Ingels, an aspiring stand-up comedian who starts neglecting her family when her career begins to take off.

"[2] Kavner has frequently appeared in Woody Allen films, having roles in Hannah and Her Sisters (1986), Radio Days (1987), New York Stories (1989), Alice (1990), Shadows and Fog (1991), the television movie Don't Drink the Water (1994)[34] and Deconstructing Harry (1997).

"[36] Kavner believes he is "a true filmmaker, one that has something to say, continually experimenting on different themes within his own film-making", adding that "anything [Allen] ever does, I always want to do, [...] I don't even have to read it.

"[37] She has done voice-over work in films such as The Lion King 1½ (2004),[38] Dr. Dolittle (1998)[39] and an uncredited role as an announcer in A Walk on the Moon (1999).

[42] She leads an intensely private life, described by The New York Times as "nearly reclusive" and "discreet and guarded beyond the usual reticent star routine".