Cecilia Beaux was born in Philadelphia, where she studied at the Pennsylvania Academy of the Fine Arts from 1877 until 1879 and with William Sartain (1843-1924) from 1881 until 1883. She also studied abroad in 1888 at the Academie Julian in Paris.
Beaux first exhibited at the Pennsylvania Academy in 1879. Her paintings continued to be shown often and received numerous awards. Her first major work, Les Derniers Jours d'Enfance, a portrait of Beaux's sister Aimee Ernesta and her nephew Henry S. Drinker, Jr., was completed in 1884, after which her paintings began to receive popular attention.
During her lifetime she was acclaimed as one of the finest American portraitists. Her awards included the Gold Medal of Honor from the Pennsylvania Academy in 1898, a gold medal at the Exposition aux Artistes Francais in 1900, and the Medal of Honor at the Panama-Pacific International Exposition in San Francisco in 1915.
Solo exhibitions of her work have been mounted at the Corcoran Gallery of Art in Washington, D.C., in 1912, at the American Academy of Arts and Letters in New York in 1935, at the Pennsylvania Academy in 1974, and at Alfred J. Walker Fine Art in Boston in 1990.
Beaux taught at the Pennsylvania Academy from 1895 until 1915, and was the first woman engaged as a full-time faculty member. In 1924 she fell and broke her hip, an injury that greatly impaired her mobility for the rest of her life. She did continue to paint afterwards, and also wrote an autobiography Background with Figures, which was published in 1930.