Acting career

Following her graduation, Davis held jobs in Chicago as a sales clerk in Marshall Field's department store and as a nurse's aide. With the help of her mother's colleagues in theatre, including Zasu Pitts, Walter Huston, and Spencer Tracy, she pursued a career as a professional actress. She first gained a part in Pitts' 1945 road tour of Ramshackle Inn, then settled in New York City. She landed the role of Si-Tchun, a lady-in-waiting, in the 1946 Broadway musical about the Orient, Lute Song, starring Mary Martin and Yul Brynner, after the show's producer told her, "You look like you could be Chinese."

After passing a screen test, she signed a seven-year contract with Metro Goldwyn Mayer Studios (MGM) in 1949; she later remarked, "Joining Metro was like walking into a dream world." Davis appeared in 11 feature films, usually typecast as a "loyal housewife", "responsible young mother", or "the steady woman". She kept her professional name as Nancy Davis even after marrying. Her film career began with minor roles in 1949's The Doctor and the Girl with Glenn Ford, and followed with East Side, West Side starring Barbara Stanwyck. She played a child psychiatrist in the film noir Shadow on the Wall (1950) with Ann Sothern and Zachary Scott; her performance was called "beautiful and convincing" by New York Times critic A. H. Weiler. She co-starred in 1950's The Next Voice You Hear..., playing a pregnant housewife who hears the voice of God from her radio. Influential reviewer Bosley Crowther of The New York Times wrote that "Nancy Davis [is] delightful as [a] gentle, plain, and understanding wife." A later critic admired the film's effort to convincingly portray Davis as pregnant—many other films from the time neglected to do so. In 1951, Davis appeared in her favorite screen role, Night Into Morning, a study of bereavement starring Ray Milland. The Times' Crowther said that Davis "does nicely as the fiancée who is widowed herself and knows the loneliness of grief," while another noted critic, The Washington Post's Richard L. Coe, said Davis "is splendid as the understanding widow." Davis left MGM in 1952, seeking a broader range of parts. She soon starred in the 1953 science fiction film Donovan's Brain; Crowther said that Davis, playing the role of a possessed scientist's "sadly baffled wife", "walked through it all in stark confusion" in an "utterly silly" film. In her last movie, Hellcats of the Navy (1957), she played nurse Lieutenant Helen Blair and shared the screen for the only time with her husband, playing what one critic called "a housewife who came along for the ride". Another reviewer, however, stated that Davis plays her part well, and "does well with what she has to work with".

Noted author Garry Wills believes that Davis was underrated as an actress overall, because her constrained part in Hellcats was her most widely seen performance. Davis seems to have downplayed her Hollywood goals: MGM promotional material in 1949 said that her "greatest ambition" was to have a "successful happy marriage"; decades later, in 1975, she would say, "I was never really a career woman but [became one] only because I hadn't found the man I wanted to marry. I couldn't sit around and do nothing, so I became an actress." Ronald Reagan biographer Lou Cannon nevertheless characterized her as a "reliable" and "solid" performer who held her own in performances with better-known actors. After her final film, she appeared in television dramas such as Wagon Train and The Tall Man until 1962, when she retired as an actress. During her career, she served on the board of directors of the Screen Actors Guild for nearly 10 years. Decades later, Albert Brooks attempted to coax Reagan out of acting retirement by offering her the title role opposite himself in his 1996 film Mother. Reagan declined in order to care for her husband, and Debbie Reynolds played the part.