Born and raised in Columbus, Georgia, Thomas moved to Washington, D.C. with her family in 1907. In 1924, she was the first graduate of Howard University's art department. In 1934, Thomas became the first African American woman to earn a Master of Fine Arts degree from Columbia University. She was also the first African American woman to have a solo exhibit at the Whitney Museum of American Art.
Thomas's early art was realistic, but delved into abstraction influenced by the work of her professors, Lois Mailou Jones and James V. Herring. Thomas's later art, influenced by Expressionism, became her best-known works: large canvases filled with irregular, brightly colored patterns. These works have been compared to Byzantine mosaics and the pointillist paintings of Georges-Pierre Seurat
Two of Thomas's works were hung in the White House. Her Watusi (Hard Edge), a work inspired by Henri Matisse's paper cutout The Snail, with colors reversed, hung in the East Wing office of First Lady Michelle Obama but was later sent back.
