Henri Masson was born in Spy, a small town near Namur in Belgium. From a young age he was drawn to painting and at the age of 13 he enrolled at the Brussels Royal Athenaeum. Following the death of his father in 1921, he emigrated to Ottawa in Canada with his mother. Upon arriving in Ottawa, Henri Masson worked in an engraver's workshop and took courses at the Ottawa Art Association and at the Ottawa Art Club. He exhibited his work for the first time in 1933 as part of a group exhibition, displaying his watercolors, pastels and drawings. In 1936 Henri Masson exhibited his first oil painting at the Ontario Society of Artists in Toronto.
His first solo exhibition was be held at the Picture Loan Society in Toronto in 1938, followed in 1939 by another solo exhibition. He also exhibited with the Canadian Group of Painters in New York and Montreal. In 1941, Masson began exhibiting at the gallery of French Art (now Galerie Valentin), was elected member of the Canadian Group of Painters and between the Canadian Society of Painters in Watercolour and the Society of Graphic Arts. In 1945 he was elected President of the Conference of Canadian Artists in Ottawa. It was only in 1945 that Henri Masson decided to finally give up his career as an engraver for prior to this, despite all of his success with his paintings, he was determined to have a steady income to support his family and children. Masson went onto become a teacher at Queens University and he later taught at the Banff School of Fine Arts.
In 1955 he received an honorary doctorate from Assumption College in Windsor, Ontario. Masson was primarily a landscape painter. He painted nature, trees, small villages, the sea, boats, lighthouses and boats. He had a particular interest in his French-Canadian heritage and his landscapes were of parts of Ottawa, Gatineau and especially the province of Quebec: Gaspé, Charlevoix (especially St. Paul's Bay) the Eastern Townships and the Laurentians. Masson primarily painted en-plein air. His oil paintings are imbued with natural and vibrant colours. His paintings iare rich in their observations of nature. Whether in his drawings, watercolors or oils, Masson had acute, but subtle, attention to detail.