Cassatt was the daughter of a banker and an affluent Pittsburgh businessman. The family moved to Paris in 1851 and also lived in Heidelberg and Darmstadt in 1853-1855. She returned to Pennsylvania in 1855 and studied at the Pennsylvania Academy of Fine Arts in Philadelphia during the years 1861 to 1865. She had studied for a short period in the studio of Charles Chaplin in Paris in 1866, while she self-taught and worked together with Gerome and Charles Bellay. She returned to America in 1870 because of the Franco - Prussian War. Then, she studied for a time at the Academy Raimondi in Parma in 1871; she imitated Correggio and Parmigianino, and admired Velazquez and Rembrandt. In the years of 1873 to 1877 she traveled to Madrid, Seville, Belgium and the Netherlands and copied Velazquez and Rubens. She finally settled in Paris in 1877, where she met Degas who advised her to join the Impressionists and she participated in the Exhibitions of 1879, 1880, 1881 and 1886, refusing to do so in 1882 when Degas did not.. Degas and Renoir greatly influenced her style of painting.

Her favorite themes are portraits of women and children. She had exhibited her works a few times at Durand-Ruel gallery and was commissioned to do a mural for the 1892 World Fair in Chicago. She traveled in the USA in 1898 and took travelling extensively in Europe and the Middle East in the following years. She was accepted into the Legion of Honour in 1904 and been awarded of a gold metal at the Pennsylvania Academy of Art in 1914. She also became a member of the National Academy of Design in New York in 1910. Her failing eyesight forced her to give up painting. She was a great practical support to the movement as a whole, both by providing direct financial help and by promoting the works of Impressionists in the USA, largely through her brother Alexander. By persuading him to buy works by Manet, Monet, Morisot, Renoir, Degas and Pissarro, she made him the first important collector of such works in America. She also advised and encouraged her friends the Havemeyers to build up their important collection of works by Impressionists and other contemporary French artists.