In 1946, at age 21, Yanofsky entered the first top-class post-war tournament, at Groningen, and defeated Soviet champion and tournament winner Mikhail Botvinnik, winning the brilliancy prize. During the next two years, he played several more European events, where his best result was second place behind Miguel Najdorf at Barcelona 1946. Yanofsky represented Canada at the Interzonals held in Saltsjöbaden 1948 and Stockholm 1962. He won the British Championship in 1953. At Dallas 1957 chess tournament, Yanofsky achieved his first grandmaster norm with wins over Samuel Reshevsky, Friðrik Ólafsson and Larry Evans. His performance at the Tel Aviv 1964 Olympiad earned him his second grandmaster norm, and the title, thereby becoming the first grandmaster raised in the British Commonwealth.