Dorothy Eugenie Brett, born November 10, 1883, was the eldest daughter of the 2nd Viscount Esher, Reginald Baliol Brett, and his wife Eleanor van de Weyer, daughter of the Belgian ambassador to the court of St. James. Besides Dorothy, called "Doll" by her family, there were two older brothers, Oliver and Maurice, and a younger sister, Sylvia. The children were raised in a restrictive manner similar to other children of the Victorian era. They saw little of their parents, being largely left in the charge of a nanny and other servants. Once the boys were sent to school, a governess was retained for the girls. However, she was dismissed after a short time and the girls' education was left to their mother.

The girls lived a fairly secluded life into their early twenties. Aside from dancing classes with the royal children at nearby Windsor Castle, under the supervision of no less than Queen Victoria, their contact with young people their own age was practically nonexistent. One friendship that they did make was with Margaret Brooke, Ranee of Sarawak, a friendship disapproved of by the Brett parents. Over ten years Dorothy formed an emotional attachment to the Ranee, and Sylvia attracted the attention of the Ranee's son, whom she later married against the wishes of her parents. The parents put an end to Dorothy's visits to the Ranee when she was 23, sending her off to their summer home in Scotland. There, General Sir Ian Hamilton, an old friend of the family, saw some of Dorothy's drawings and persuaded her parents that she should attend the Slade School of Art.

Dorothy Brett was accepted into the Slade School, on a provisional basis, in the fall of 1910. Fellow students at the time included Dora Carrington, Mark Gertler, and David Bomberg. In the tradition of the school, all students dropped their given names and went by their surnames, and so Dorothy became Brett to everyone but her family and went by that name for the rest of her life. Brett completed the four year program at Slade, winning several prizes and honors in her sojourn there.

At the end of her second year, Brett's father set her up in a studio of her own, partly to help her artistically and partly to move her out of the family home in town where the servants had begun to complain about the "goings on" of Brett's artistic friends.

Several important events took place in Brett's life during her school years. She began to develop the auditory problems that would leave her dependent on hearing aids for the rest of her life. She became friends with Gertler and Carrington, and through Gertler she became acquainted with Augustus John, and, in 1914, she met Lady Ottoline Morrell. In October of 1915 Brett met D. H. Lawrence and his wife Frieda.

Over the next several years Brett spent a great deal of time at the Morrell's Garsington Manor near Oxford along with members of the Bloomsbury group. She seems to have developed a crush on Ottoline which led to voluminous correspondence but little else. In 1919 Brett's parents helped set her up in a house in Hampstead, London, arranged for an annual allowance, and made a final effort to push her into independence.

In 1923 D. H. and Frieda Lawrence returned to England from North America, thus setting in motion the second phase of Brett's life. Lawrence had been proposing the creation of a community called Rananim for several years without success. He felt that he had found the perfect location for such a spot in Taos, New Mexico, and was now actively seeking members. Only John Middleton Murry and Brett seriously considered the idea and in the spring of 1924, only Brett joined the Lawrences on the Aquatania bound for New York.

Taos became Brett's home. Though she traveled frequently to Mexico, New York, and even made a few trips back to Europe, her roots were firmly planted in New Mexico. She developed a strong emotional attachment to D. H. Lawrence, and after Lawrence's death continued to live near Frieda for the remainder of Frieda's life. Mable Dodge Luhan, another prominent figure in Taos, also played an important role in Brett's life, alternating between protector and antagonist.

In New Mexico Brett painted Native Americans. She was permitted to visit the Taos Pueblo for important ceremonies and then transferred the images to canvas, creating a series of paintings for which she is perhaps best known, the Ceremonials. Her close relationship to D. H. Lawrence made her popular with the researchers who sought to better understand his life. She lived to within a few months of her 94th birthday, dying on August 24th, 1977.