Oscar Cahén was born in Copenhagen, Denmark, 1915. He studied at the Dresden Kunstakademie where he completed his Master of Fine Arts, as well as attended art schools in Paris, Italy, and Stockholm. In 1938, he was instructor of illustration and design at the Rotters Studio in Prague. His father was an outspoken opponent of the Nazis and for that reason had to flee to the United States. In 1938, under threat of arrest, Oscar and his mother had to flee as well, escaping to London, England, where Oscar worked as a freelance illustrator.

In 1939, he was interned as an enemy alien and in 1940 was given the choice of either remaining interned in the United Kingdom or being shipped to Canada or Australia. He chose Canada and ended up in an internment camp near Sherbrooke. He was released in 1942 and did freelance work for the Montreal Standard and Rapid Grid and Batten in Montreal. In 1944, he moved to Toronto and finally to Oakville, where he settled with his wife and son. He became director for Magazine Digest in Toronto that year, but returned to do freelance work for New Liberty, Playtime, Chatelaine, and MacLean's magazine.

By the mid-50's, he had become a highly successful illustrator, but favoured abstraction in his personal work. Cahén delighted in using vibrant, even violent colour juxtapositions. In 1954, he became a founding member and inspirational power behind Painters Eleven, which was recognized as leader of non-objective painting in English Canada as was the Non-Figurative Artists Association of Montreal for French Canada.

Tragically, his life ended when on the evening of November 26, 1956, his sportscar collided with a gravel truck, less than a mile away from his Elmhurst Avenue home.