Genealogical research which was conducted after her death revealed that she and Lizzie Borden, acquitted of the murder of her father and stepmother in 1893, were sixth cousins once removed; both of them were descended from 17th-century Massachusetts resident John Luther.

In October 1953, Montgomery made her Broadway debut, starring in Late Love,[6] for which she won a Theater World Award for her performance.

[6] Montgomery's early career consisted of starring roles and appearances in live television dramas and series, such as Studio One, Kraft Television Theater, Johnny Staccato, Burke's Law, The Twilight Zone, The Eleventh Hour, Wagon Train, Boris Karloff's Thriller, and Alfred Hitchcock Presents.

[8] Montgomery was featured in a role as a socialite who falls for a gangster (Henry Silva) in Johnny Cool (1963), directed by William Asher, and the film comedy Who's Been Sleeping in My Bed?

[citation needed] As a consolation to ABC, Montgomery and Asher (under their company name Ashmont, which produced Bewitched) offered a half-hour sitcom, The Paul Lynde Show, to the network for the 1972–1973 season.

In a parody of her Samantha Stephens role, she made a cameo appearance as a witch at the end of the beach party film How to Stuff a Wild Bikini (1965).

Montgomery returned to Samantha-like twitching of her nose and on-screen magic in a series of Japanese television commercials (1980–1983) for "Mother" chocolate biscuits and cookies which were produced by the confectionery conglomerate Lotte Corp.

[12] Montgomery later played a pioneer woman facing hardship in 1820s Ohio in the miniseries The Awakening Land (1978), for which she earned her ninth Emmy nomination.

In the television film Amos (1985), she played a rare villainous role, as a vicious nurse who abuses her wards in a home for senior citizens.

[22] She was also an ardent critic of the Vietnam War, she supported Robert F. Kennedy's presidential campaign in 1968,[23] and in later years, she was an active advocate of AIDS research and outreach to the disabled community.

[24] Professionally, she lent her voice as the narrator of two political documentaries which were critical of U.S. foreign policy, Cover Up: Behind the Iran Contra Affair (1988) and its Academy Award-winning sequel The Panama Deception (1992).

[25] In June 1992, Montgomery and Dick Sargent, her former Bewitched co-star as well as her good friend, were grand marshals at the Los Angeles Gay Pride Parade.

[11] During the last year of her life, Montgomery volunteered at the Los Angeles Unit of Learning Ally, a nonprofit organization which records educational audio books for disabled people.

[26] In 1994, Montgomery produced several radio and television public-service announcements for Learning Ally's Los Angeles unit.

[citation needed] On June 3, 1995, sixteen days after her death, Learning Ally's Los Angeles unit dedicated its 1995 Record-A-Thon to Montgomery.

[29] With no hope of recovery and unwilling to die in a hospital, Montgomery chose to return to her Beverly Hills home that she shared[11] with Foxworth.

Herbie Hancock played music, Amanda McBroom sang, and Dominick Dunne spoke about the early years of their friendship when both of them lived in New York City, while Foxworth read many of the sympathy cards sent by fans.