Spring Byington was born in Colorado Springs, Colorado, the daughter of Helene Maud (née Cleghorn 1862-1907) a doctor, and Edwin Lee Byington (1852–1891), an educator and Superintendent of schools in Colorado. Byington had one sibling, a younger sister, Helene Kimball Byington. After Edwin Lee died, their mother decided to send her younger daughter, Helene, to live with her parents, Arthur and Charlotte Cleghorn, in Port Hope, Ontario, while Spring remained with family in Denver. Her mother moved to Boston and became a student at the Boston University School of Medicine, where she graduated in 1896. After graduation, she moved back to Denver and began a practice with fellow graduate, Dr. Mary Ford. Byington played in amateur shows in her school days and graduated from North High School in 1904. Shortly afterward, at age 14, Byington became a professional actress with the Elitch Garden Stock Company. Her mother had been a friend of Mary Elitch. When their mother died in 1907, Byington and Helene were legally adopted by their aunt Margaret Eddy. Byington stated in an interview in 1949 that she had tried her hand at newspaper reporting. However, as she was already of legal majority age, she took her inheritance to begin an acting career in New York City, saying that she enjoys it, and “I can’t do anything else very well.”

In 1908, Byington joined a repertory company that was touring Buenos Aires, Argentina. Between 1908 and 1916, the company performed American plays translated into Spanish and Portuguese in Argentina and Brazil. Upon returning to New York, Byington divided her time between working in Manhattan and staying with her daughters. Her daughters were living with friends J. Allen and Lois Babcock, in Leonardsville Village, New York (Madison County), who were taking care of them while Byington worked in the city. She began touring in 1919 with a production of Birds in Paradise, which brought the Hawaiian culture to the mainland, and in 1921 began work with the Stuart Walker Company, for which she played roles in Mr. Pim Passes By, The Ruined Lady and Rollo’s Wild Oats, among others. This connection landed her a role in her first Broadway performance in 1924, George S. Kaufman and Marc Connelly’s Beggar on Horseback which ran for six months. She renewed the role in March and April 192, and continued on Broadway with an additional 18 productions in the ten years from 1925 to 1935. These included roles in Kaufman and Moss Hart’s Once in a Lifetime, Rachel Crothers’s When Ladies Meet, and Dawn Powell’s Jig Saw.

In her last years on Broadway, Byington began work in films. The first was a short film titled Papa’s Slay Ride (1930), where she played the role of “Mama,” and the second role, and better known, was in Little Women (1933) as “Marmee,” with Katharine Hepburn as her daughter “Jo”. For MGM, she played Midshipman Roger Byam’s (Franchot Tone) mother in Mutiny on the Bounty (1935). She became a household name during The Jones Family series of films, and continued as a character actress in Hollywood for several years. Byington was nominated for the Academy Award for Best Supporting Actress for You Can’t Take it with You (1938), which was won by Fay Bainter for Jezebel (in which Byington also had a role as antebellum society matron, Mrs. Kendrick). During World War II, Byington worked in radio, and decided to continue working in this medium as her film career began to decline after the war. In 1952, she joined CBS Radio to become the lead role of the widowed Lily Ruskin, in the sitcom December Bride. In 1954, the television company Desilu Productions produced a pilot of the show for a sitcom, also starring Byington. The pilot was successful, and the new hit sitcom aired in its first two seasons immediately following I Love Lucy. December Bride broadcast 111 episodes through 1959. Byington guest starred as herself in the CBS sitcom Dennis the Menace, starring Jay North, in the episode titled “Dennis Birthday” (1961), with character actor Vaughn Taylor also appearing in this segment.

From 1961 to 1963, Byington was cast as the wise, matronly housekeeper, Daisy Cooper, in the NBC Western series Laramie, starring John Smith and Robert Fuller. On Laramie, Daisy serves as a surrogate grandmother to orphaned Mike Williams, played by the child actor Dennis Holmes. After Laramie, Byington guest starred as Mrs. Jolly on Dennis Weaver’s NBC sitcom, Kentucky Jones, and as wealthy J. Pauline Spaghetti in an episode of “Batman” in 1966. Her penultimate role before her death from cancer was in 1967, as Larry Hagman’s mother on NBC’s I Dream of Jeannie. Her final role was in 1968 as Mother General on ABC’s The Flying Nun, starring Sally Field. Byington spoke some Spanish, which she learned during the time spent with her husband in Buenos Aires; and she studied Brazilian Portuguese in her Golden Years. In July 1958, she confided to reporter Hazel Johnson that she had acquired a “small coffee plantation” in Brazil the month before and was learning Portuguese. “Miss Byington explained that she first listens to a ‘conditioning record’ before she goes to sleep. An hour later, her Portuguese lessons automatically begin feeding into her pillow by means of a small speaker.” Byington was fascinated by metaphysics and science fiction novels, including George Orwell’s 1984. She surprised her co-stars in December Bride with her knowledge of the Earth’s satellites and the constellations in the night sky. In August 1955, Byington began taking flying lessons in Glendale, California; but the studio made her stop because of insurance problems. In January 1957, she testified in the trial of the Sica brothers as a character witness in behalf of the DaLonne Cooper, who was a friend and the Script Supervisor for December Bride. On September 7, 1971, Byington died of rectal cancer  at her home in the Hollywood Hills. At her request, her body was donated to medical research. For her contribution to the film and television industry, Byington has two stars on the Hollywood Walk of Fame, one for films at 6507 Hollywood Blvd., and one for television at 6233 Hollywood Blvd.