In 1963, Aibileen Clark is an African-American maid in Jackson, Mississippi. She works for socialite Elizabeth Leefolt, caring for her daughter Mae Mobley, whom Elizabeth neglects. Aibileen's best friend and fellow maid Minny Jackson works for Mrs. Walters, whose daughter Hilly Holbrook leads the women's socialite group and is president of the city's Junior League chapter.

Elizabeth and Hilly's mutual best friend Eugenia "Skeeter" Phelan, a recent graduate of Ole Miss and an aspiring writer, is uncomfortable with her town's racist attitudes toward their maids, including Hilly's insistence on installing separate bathrooms for the help due to the belief that they carry "different diseases". Skeeter lives with her parents at Longleaf, their cotton plantation. Skeeter learns that her mother Charlotte fired Constantine, the maid who raised her, and decides to write a book of interviews with African-American maids working for white families.

Minny is soon fired by Hilly for using the guest bathroom during a storm and rendered unemployable due to Hilly's lies, but finds a job as a housemaid for Celia Foote, a housewife ostracized by the socialites. Celia treats Minny with respect and they become friends, but keeps Minny's employment secret from Celia's husband Johnny, Hilly's former beau. Celia suffers a miscarriage, and she reveals to Minny that she never told Johnny about the pregnancy, including two previous miscarriages she had.

Skeeter reaches out to Aibileen, who eventually agrees to be interviewed, as does Minny. Elaine Stein, Skeeter's editor at Harper & Row, tells her that stories of two maids are not enough, but fear of retribution prevents other maids from coming forward. Aibileen tells Skeeter about her struggle to cope with the death of her only son, and believes the book will help her find closure.

Hilly refuses to advance money to her replacement maid, Yule May, who is struggling to send her twin sons to college. Yule May discovers a lost ring under a sofa and pawns it, but is later brutally arrested as Hilly watches. This incident and the local assassination of Medgar Evers inspire more maids to tell Skeeter their stories.

Following the assassination of John F. Kennedy, Skeeter, Aibileen, and Minny fear the maids' stories will be recognized. Minny reveals the "terrible awful" as a form of insurance: after her termination, Minny brought Hilly her famous chocolate pie but revealed – after Hilly had finished two slices – that she had baked her own excrement into it; Hilly later forced her mother into a nursing home for laughing at her during the incident. The inclusion of this in the book prompts Hilly to crusade in denial that the book is about people in Jackson.

Skeeter confronts her mother about having fired Constantine after a lifetime of service, and Charlotte confesses that during a Daughters of America luncheon, she fired Constantine to save face because Constantine's daughter Rachel embarrassed Charlotte by disobeying her orders to enter through the kitchen. Rachel took Constantine to Chicago, where she later died. Charlotte feels guilty that she was not brave enough to stand up for someone who had served her for two decades and helped raise her daughter.

The book is published anonymously and is a success. Minny reveals the "terrible awful" to Celia, who finally sees what a manipulative bully Hilly is, and writes a check to one of Hilly's charity groups, made out to "Two Slice Hilly". Incensed, Hilly threatens to su