Thérèse Lessore was born in Brighton and began her artistic training at the Slade School of Fine Art in 1904. Lessore came from an artistic family, her father having been an accomplished watercolourist and her grandfather, a designer for Wedgwood. She excelled at the Slade, and was awarded the Melville Nettleship Prize for Figure Composition. Lessore exhibited often with the London Group, of which she was a founding member, and the New English Art Club along with galleries such as the Goupil in London. She held her first solo exhibition at the Eldar Gallery in 1918. She later married the artist Walter Sickert, a popular figure of the London art scene.