Guido Molinari was born in 1933 in Montreal into an artistic family - his father was a musician and his mother the daughter of a craftsman. In 1951, Guido Molinari began studying at the School of Art and Design at the Montreal Museum of Fine Arts, where he distinguished himself with his protests against the accepted concepts of painting by painting blindfolded.

Although working in abstraction and aware of the Automatist and the Plasticien painters in Montreal, Molinari did not directly align himself with these groups. Interested in the explorations of European Surrealists in automatic writing, his work in the early 1950s reflected his own experiments with this practice. However, Molinari declared his freedom by describing himself as the theorist of "Molinarism." He was a charismatic intellectual and a central figure in the art scene in Montreal and its new directions into abstraction. His first solo show was at l'Échourie, where he was director of exhibitions. His intent was to make l'Échourie a meeting place for artists of the post-Automatist generation. In 1955 he founded Galerie l'Actuelle, the first gallery in Montreal to exclusively show abstract art. In 1956 the Non-Figurative Artists Association of Montreal was created at Galerie l'Actuelle, and Molinari, a founding member, participated in their exhibitions. During the 1950s, as well as works based on automatic writing, Molinari produced gestural paintings, and a powerful group of black and white works. In 1959 he was included in the Third Biennial Exhibition of Canadian Art at the National Gallery of Canada.

In the 1960s, he created geometric abstract works and produced his Stripe Paintings series. During this decade he exhibited in galleries and museums in New York - such as the Guggenheim Museum and the Museum of Modern Art (The Responsive Eye in 1965), and in 1963 MOMA acquired one of his paintings. He began to exhibit internationally, and continued to do so in subsequent decades.

Molinari's interest in the dynamic energy of colour continued in his Quantifier series - large-scale monochromes, in radiant hues such of red or cobalt blue, with subtle and irregular divisions created by subtle tonal differences - begun in 1975, this series endured over 20 years.

Molinari taught for 27 years at Sir George Williams University (now Concordia University), retiring in 1997. His theoretical writing influenced generations of younger Canadian artists. He won many awards, such as the Guggenheim Fellowship in 1967 and the Prix Paul-Émile Borduas in 1980. He represented Canada in the 1968 Venice Biennale with works from his Bi-serial series, winning the David E. Bright Foundation prize. Retrospectives of his work took place in 1976 at the National Gallery of Canada, and in 1995 at the Musee d'art contemporain de Montreal. He died in Montreal in 2004.