She first attended the Cooper Union School of Design in 1866, studying there until 1870 with William Rimmer, Edwin Forbes, Robert Swain Gifford and George Edmund Butler. There, she took classes with her friend Helena de Kay. From 1871 to 1875 she studied at the Antique School of National Academy of Fine Arts, during which time she shared an apartment with de Kay and took painting lessons from the painter John La Farge. He specialized in Japanese aesthetics and was said by Dewing to have created paintings that were “the most beautiful in all the world” and greatly influenced her own work. As a student she had already begun to gain a reputation as a capable painter, her works attracted “much attention for its broad, vigorous brush work, and rich, glowing color” and were exhibited at the National Academy of Design. In 1875, Oakey and other students from the academy left to establish the now renowned Art Students League of New York. The same year her works were exhibited at a show organized in New York by La Farge and she studied with landscape artist William Morris Hunt and in 1876 with Thomas Couture.