Anna Sewell was born on 30 March 1820 in Great Yarmouth, Norfolk, England, into a devoutly Quaker family. Her father was Isaac Phillip Sewell (1793–1879), and her mother, Mary Wright Sewell (1798–1884) was a successful author of children's books. She had one sibling, a younger brother named Philip and was largely educated at home.
When she was twelve, the family moved to Stoke Newington where she attended school for the first time.
Two years later, however, she slipped while walking home from school and severely injured her ankles. Her father took a job in Brighton in 1836, in the hope that the climate there would help to cure her. Despite this, and most likely because of mistreatment of her injury, for the rest of her life she could not stand without a crutch or walk for any length of time. For greater mobility, she frequently used horse-drawn carriages, which contributed to her love of horses and concern for the humane treatment of animals.