Leon Bellefleur was born in Montreal on february 8, 1910. His father objected to his desire to study at Beaux Arts. After graduating from École normale Jacques-Cartier, he starts his career as a school teacher which will last for twenty-five years. He marries Rita Jolicoeur in 1934. They have five children together. He starts making drawings before he is ten years old. Eventually, he goes into painting. In 1946, he holds his first exhibition presented along with the drawings of the children he is teaching to.
The following year, he publishes "Plaidoyer pour l'Enfant". (Plea in favour of children). In 1951, he wins the first prize for modern painting at the Spring Exhibition of the Fine Arts Museum of Montreal. He previouly held an exhibition at The Agnès Lefort Gallery. He also participated in a collective exhibition of young artists in Europe and to the Sao Paulo Biennial.