The son of a farmer, Charles Dewey evinced artistic proclivities in his youth. Because his family did not support his interest, he worked as a janitor to pay for painting supplies. In 1869 Dewey entered the National Academy school, working in the antique class his first year; the next two years he was enrolled in both the antique and life classes. Although he clearly was doing well (receiving honorable mentions for his work in the antique in both 1871 and 1872), he was absent for the academic year 1872-73. But he returned in the autumn of 1873 for two more years of study. He again registered in both the antique and life classes for the 1881-82 school year, suggesting a somewhat unusual desire to brush up on his basic training sometime after he had established his career. It is likely that Dewey met Albert Pinkham Ryder when the latter entered the Academy's antique class in 1870 and that their lifelong friendship began at this time; Dewey was the executor of Ryder's estate.
Beginning in 1876, Dewey spent two years in the Parisian atélier of Emile Carolus-Duran and helped his French master with decorations for a ceiling in the Louvre. He also worked at the Gobelin tapestry studios. Upon returning to New York in 1878, Dewey opened his studio, where he also gave painting lessons. He became a member of the Society of American Artists the next year. Dewey's first appearance in an Academy annual exhibition was in 1876. He did not show in an annual again until 1879, following his return from Europe; thereafter he was regularly represented through 1893 and from 1904 until the year he died. Dewey moved his studio and home to New York's Chelsea Hotel in 1886, remaining there to the end of his life.
Although Dewey worked in portraiture, he was best known for his tonal landscapes, bathed in the poetic light of dawn or dusk. He generally favored American scenery as the basis for these compositions but also painted during several summer trips to the English countryside.