Belarski was a self-taught artist, but at age 21 he put himself through Pratt Institute in Brooklyn by working at odd jobs. He won a number of art competitions while at Pratt. In 1929 he was invited back to Pratt to teach.
During the same period he sold artwork to Dell for its war pulp magazines.
In the 1950s Belarski became one of the leading artists of paperback book covers, doing most of his work for Popular Library.
In 1957 he joined the staff of the Famous Artists School, teaching courses in commercial art.