Achsah Barlow Brewster was born in New Haven, Connecticut in 1878. She graduated from Smith College in 1902 and moved to New York City where she studied at the New York School of Art and at the Art Students League with Robert Henri. In 1905 she went to Paris to study from live models at artist estatess of Lucien Simon and Castellucio. In 1904 she was introduced to the artist, Earl H. Brewster, by the author Vachel Lindsay, who thought she looked just like the woman in a magazine cover painted by Brewster. Earl and Achsah fell in love and married in 1910.

After their wedding, the Brewsters went to Europe and never returned to the United States except for a brief visit in 1923. In Paris in 1912 Achsah gave birth to a daughter, Harwood, who became the subject of many of Achsah's paintings. Until late 1935 the Brewsters lived a somewhat nomadic life moving frequently from one place to another, mostly in France and Italy. They also traveled to Ceylon and India. They knew many of the well-known artists and writers of the time including D. H. Lawrence and Willa Cather. Shortly before Harwood was married in 1936, they moved to Almora, India. Aschsah died there in 1945.

It has been noted that Achsah's art was a search for spirituality and that her figures relate to the landscpe with a simplicity that recalls the Italian primitives. Her work has been compared to that of Puvis de Chavannes and Paul Gauguin. Her paintings were exhibited in Paris at the Galerie Cheron and the Grand Palais and in Rome at the Secessione. In India they were exhibited at the Roerich Centre of Art and Culture in Allahabad. Many of her paintings were purchased for various churches, colleges, public buildings and homes in Europe, the United States and India. One was recently acquired by the San Francisco Museum of Fine Arts