Robert Gagen was born in London, England in 1847. He came to Canada with his parents in 1862. The family settled in Seaforth, Ontario. Gagen studied under William Nichol Cresswell. Gagen sent paintings to provincial exhibitions, where he was awarded various prizes.
He moved to Toronto and studied under G. Gilbert, followed by employment at Notman and Fraser a notable photography and design. He received instruction from noted artist John A. Fraser. He spent nine years with the firm painting watercolours on a photographic base. Fraser also taught him about landscape painting.
He was a founding member of the Ontario Society of Artists in 1872 and later became the society’s permanent secretary. He became an associate member of the Royal Canadian Academy at its founding in 1888 and was elected a full member in 1915. He was a member of the Arts and Letters Club in Toronto and served as Commissioner of Fine Arts for the Canadian National Exhibition from 1912-1926. He was awarded honourable mention at the Pan-American Exhibition in Buffalo, New York in 1901.
The National Gallery of Canada has several of his paintings in their permanent collection.
He died in 1926.