Frank Johnston was born in 1888 in Toronto, and studied at the Ontario College of Art under William Cruikshank and G.A. Reid. In 1911, he began working at the commercial art firm Grip Ltd. in Toronto, which proved to be an influential meeting place for the future of Canadian art, as the firm employed five of the seven artists who would form the iconic Group of Seven - Johnston, J.E.H. Macdonald, Frederick Varley, Arthur Lismer and Franklin Carmichael. Although in close contact with his colleagues, Johnston strongly remained an individual, a trait that he would exhibit throughout his career.
Beginning in 1912, Johnston spent three years in the United States, studying at the Pennsylvania Academy of Fine Art and working at Carleton Studios in New York before returning to Toronto in 1915. In 1918, Johnston was commissioned to document the Royal Flying Corps at their training camps in Ontario, as part of the Canadian War Memorials during World War I. In fall of that same year, Johnston joined fellow Group members Lawren Harris and Macdonald in the first boxcar expedition up the Algoma Central Railway in northern Ontario. He joined Group members on two more Algoma sketching trips in 1919 and 1920. The Group of Seven held their first official show in 1920 at The Art Gallery of Toronto, now the Art Gallery of Ontario. At this pivotal exhibition, Johnston exhibited and sold more paintings than any other Group member.
In December of 1920, Johnston held an independent exhibition at The Fine Art Galleries, T. Eaton Co. Ltd. in Toronto. In 1921, he moved to Manitoba to accept the position of Principal of the Winnipeg School of Art and began a gradual departure from the Group, and transformed his style to a more realistic one. Johnston returned to Toronto in 1924 to teach at the Ontario College of Art, and then officially resigned from the Group. Johnston claimed there were no problems between him and the other members, but that he simply preferred to follow his own path. During this process, he changed his first name to Franz. As well as painting in oil, Johnston was known for his accomplished use of the medium of tempera. His work proved to be popular with the public, and at a time when many Canadian artists stuggled to support themselves through their art, Johnston attained substantial financial success.
Johnston developed larger narrative paintings in the 1930s and 1940s, in addition to his more intimate examinations of landscape. During this time his subjects ranged from the pastoral countryside of Ontario to northern Quebec and the Northwest Territories. Johnston continued to paint until passing away on July 9, 1949 in Toronto.