Born in Stockbridge, Massachusetts, she was the daughter of a prosperous lawyer and successful politician, Theodore Sedgwick, who later became a judge of the Massachusetts Supreme Judicial Court and Speaker of the United States House of Representatives. She was sent to study at a finishing school in Boston, and as a young woman she took charge of a school in Lenox. Sedgwick's conversion from Calvinism to Unitarianism led her to write a pamphlet denouncing religious intolerance that evolved into her first novel, A New-England Tale.

In 1827, her third novel Hope Leslie recounted a dramatic conflict between British colonists and Native Americans. The book earned a large readership and made her one of the most talked-about female novelists of the day. Sedgwick's writings involved American settings, combining patriotism with protestations against Puritan oppressiveness. Her topics would become important to the creation of a national literature enhanced through her detailed descriptions of nature. Although moralistic, Sedgwick created spirited heroines who, as the focal point of her stories, did not conform to the stereotypical conduct of women at the time. In her later work, Married or Single, she put forth the bold idea that women should not marry if it meant they would lose their self-respect.

Much in demand, from the 1820s to the 1850s Catharine Sedgwick made a good living writing short stories for a variety of periodicals. Following her death in 1867, by the end of the 19th century she had been relegated to near obscurity. Interest in her works and an appreciation of her contribution to American literature was largely stimulated by the advent of low-cost electronic reproductions that became available at the end of the 20th century.

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