Denis Juneau was born in Verdun, Québec in 1925. He studied art at Montréal’s Monument National for one year in 1942 and École des beaux-arts from 1943–1950, where he was taught by Sylvia Daoust, Armand Filion, Alfred Laliberté and Alfred Pellan. He also completed an apprenticeship in goldsmithing with Georges Delrue in 1951–1952, and an internship as a designer under Gilles Beaugrand in 1952.
From 1954 to 1956, Juneau studied industrial design at the Centro Studi Arte/Industria in the city of Novara, under the supervision of the school’s founder, painter and designer Nino di Salvatore.
He returned to Montréal, in 1957 and exhibited as part of a group show at Galerie Denyse Delrue, he also had his first solo exhibition in 1958 at this same gallery. Juneau participated in the 1959 exhibition organized by Fernand Leduc entitled 'L’Art abstrait'.
Juneau’s work has been exhibited in Canada, New York, Washington, Paris, London, Brussels and Spoleto.
His work has travelled to institutions such as the National Gallery of Canada, and The Musée du Québec, among others.
Juneau has been the recipient of a number of honours, including the 1986 Gershon Iskowitz Foundation Prize and the 2008 Paul-Émile-Borduas Award, and membership in The Royal Canadian Academy of Arts.
He lives and works in Montréal.