George Agnew Reid was born in 1860 to a farming family in Wingham, Ontario. He showed an early interest in art and eventually, despite his father's initial disproval, became an art student under Robert Harris at the Ontario School of Art in 1879 in Toronto. He continued his art education at the Pennsylvania Academy of Fine Arts under American Realist Thomas Eakins, who taught anatomy and life drawing, then in 1889 traveled to Paris, and attended the Académie Julien and the Académie Colarossi in Paris. While there, his work was shown at the Paris Salon. He and his wife, fellow artist Mary Hiester, traveled and painted frequently to Europe, the United States, and throughout Canada.

Upon settling in Toronto in 1886, Reid began teaching private art classes in his home, in addition to continuing with his own artwork. Reid's early work was in the academic style of figure painting, often large, such as his 1890 work Mortgaging the Homestead. After his 1896 trip to Paris, his interest in landscape painting grew, and his exposure to the Impressionists brought more light, colour and a more open brush-stroke into his work. Later, his landscapes grew darker and more tradition in composition.

Reid's first exhibition was in 1888 at Oliver, Coate & Co. in Toronto, followed by an exhibition in 1894 with five American painters at American Art Galleries, New York. Reid became the first principal of the newly formed Ontario College of Art in 1912, and continued in the post until 1918. He was commissioned as a war artist in 1918, and designed a new building for the Ontario College of Art in 1920. He became a member of the Royal Academy of Arts in 1989, and later served as its president. After his retirement from the College in 1929, Reid painted many murals for public and private collections, such as the Jarvis Collegiate and the Royal Ontario Museum of Paleontology. His work is held in public collections across Canada. Reid died in Toronto in 1947.