Sarah Jessica Parker was born in Nelsonville, Ohio, the daughter of Barbara Parker (née Keck), a nursery school operator and teacher, and Stephen Parker, an entrepreneur and journalist. She was one of a total of eight children from her parents' marriage and her mother's second marriage (her full siblings include actors Timothy Britten Parker and Pippin Parker). After her parents' divorce, her mother married Paul Forste, a truck driver and account executive who was a part of Parker's life from an early age. Sarah Jessica Parker's father, a native of Brooklyn, was of Eastern European Jewish background; his family's original surname was "Bar-Kahn" ("son of Kohen"). Parker's mother was of English and German descent; through her mother, Parker is descended from Esther Elwell, one of the accused during the Salem witch trials. Sarah Jessica Parker has identified culturally and ethnically with her father's religion, Judaism, although she has had no religious training. She has said that even while her family lived in Cincinnati, her mother emulated a New York lifestyle.
As a young girl, Parker trained in singing and ballet, and was soon cast in the Broadway revival of William Archibald's The Innocents. Her family moved to Cincinnati, Ohio and then to Dobbs Ferry, New York, near New York City, so that she could get specialized training. There, her mother and stepfather helped Parker develop her career as a child actress. In 1977, the family moved to the newly-opened planned community on Roosevelt Island, in the East River between Manhattan and Queens, and later to Manhattan. The family later moved to Englewood, New Jersey, where Parker attended Dwight Morrow High School.
Sarah Jessica Parker attended the School for Creative and Performing Arts in Cincinnati, the School of American Ballet in New York City, Dwight Morrow High School in New Jersey, and the Professional Children's School, Hollywood High School in Los Angeles, California.