She was born Marilyn Katz in Brooklyn, New York and studied psychology and English at New York University. She and her husband Alan Bergman, whom she married in 1958, were born in the same hospital and raised in the same Brooklyn neighborhood, but their first meeting did not take place till each had relocated to Los Angeles. Together they have written the music and lyrics for numerous television shows, films, and stage musicals. One of their early successes was "Sleep Warm" the title track to Dean Martin's 1959 album on which Frank Sinatra was the 'guest' conductor. Sinatra sang his first of their compositions, "Nice 'n' Easy", on his 1960 album Nice 'n' Easy.
Bergman was inducted into the Songwriters Hall of Fame in 1980. In 1986 she was awarded the Women in FilmCrystal Award for outstanding women who, through their endurance and the excellence of their work, have helped to expand the role of women within the entertainment industry. In 1995 she was awarded an honorary doctorate by the Berklee College of Music. The following year, she received France's highest cultural honor, the Commander of the Order of Arts and Letters medal.
She served as president and chairman of the board of the American Society of Composers, Authors and Publishers (ASCAP), the world's foremost performing right organization, for fifteen years. Bergman was elected in April 1994 after five terms as the first woman ever to serve on ASCAP's board of directors. Marilyn completed her term as president in April 2009, but continues to serve on ASCAP's Board.