Davis achieved prominence for her role in The Bob Cummings Show for which she twice won the Emmy Award for Outstanding Supporting Actress in a Comedy Series. She later played the part of Alice, the housekeeper in The Brady Bunch series.

Davis's first success was as Charmaine "Schultzy" Schultz in the sitcom The Bob Cummings Show on NBC. She auditioned for the role because her friend's boyfriend was a casting director and recommended her for the part. She won the Emmy Award for Outstanding Supporting Actress in a Comedy Series twice out of four nominations for this role. On February 9, 1960, Davis received a star on the Hollywood Walk of Fame.

In the 1965–1966 television season, she appeared as Miss Wilson, a physical education teacher at a private girls' academy in San Francisco, in John Forsythe's NBC sitcom The John Forsythe Show. For a period in the 1960s and 1970s, Davis was known for her appearances in television commercials for the Ford Motor Company, particularly for the mid-sized Ford Fairlane models. Davis was featured in commercials for Minute Rice until the mid-1980s.

From 1969 to 1974, Davis played housekeeper Alice Nelson in The Brady Bunch television series. Since then, she has returned to take part in various Brady Bunch TV movies, including The Brady Girls Get Married (1981) and A Very Brady Christmas (1988). She also reprised her role as Alice Nelson two short-lived Brady Bunch spin-off television series: The Brady Brides (1981) and The Bradys (1990), both of which lasted only six episodes. She also made a cameo appearance as a truck driver named "Schultzy", a reference to her days on The Bob Cummings Show, in The Brady Bunch Movie in 1995.

In the early 1990s, Davis focused on theater. She performed in a production of Arsenic and Old Lace, and a world tour production of Crazy For You.

Davis never completely retired from acting; in her later years she appeared in several disposable mop commercials featuring famous television domestics, and has appeared in a number of Brady Bunch reunion projects, most recently TV Land's The Brady Bunch 35th Anniversary Reunion Special: Still Brady After All These Years. On April 22, 2007, The Brady Bunch was awarded the TV Land Pop Culture Award on the 5th annual TV Land Awards. Davis and other cast members accepted the award, and she received a standing ovation.

Davis was born in Schenectady, New York, the daughter of Marguerite (née Stott) and Cassius Miles Davis. She has an identical twin, Harriet, and an older brother Evans.

When Davis was three, she and her family moved to Erie, Pennsylvania. She graduated from Strong Vincent High School, and is a graduate of the University of Michigan. She originally enrolled in the University of Michigan as a pre-med major, however, she changed her mind and went into drama after seeing her older brother's performance of Oklahoma! Davis graduated from the University of Michigan in Ann Arbor in 1948 with a degree in drama and speech.

In 1976, she sold her home in Los Angeles to move to Denver, Colorado, where she joined an Episcopal community led by Bishop William C. Frey. The community later relocated to Ambridge, Pennsylvania. As of 2008, she lived near Leon Springs, Texas in a religious community.

Vivian Vance (1953) · Audrey Meadows (1954) · Nanette Fabray (1955) · Pat Carroll (1956) · Ann B. Davis (1957) · Ann B. Davis (1959) · Alice Pearce (1966) · Frances Bavier (1967) · Marion Lorne (1968) · Karen Valentine (1970) · Valerie Harper (1971) · Sally Struthers/Valerie Harper (tie) (1972) · Valerie Harper (1973) · Cloris Leachman (1974) · Betty White (1975)