He was the son of a barber who worked in Toronto to make his living. During World War I, he went to a Business College, because his eyesight was bad enough for the army to reject him. He went to Manitoba after the war to become a farmer, but he only did that briefly. He traveled to Toronto again, where he held several jobs at different times; one of which was selling radios. However, he found selling radios difficult because the only district left for him to work in was northern Ontario. By quite a stroke of luck, he was able to procure a radio frequency and transmitter for $201. CFCH North Bay officially went on the air on March of 1931. He sold radios for quite some time after that, but his focus gradually shifted to his radio station, rather then the actual radios.
He then built up his North American press and radio holdings before acquiring his first British newspaper, The Scotsman, in 1952, the year he settled in Britain. By the mid-1960s the Thomson Organization had become an international corporation, with interests in publishing, printing, television, and travel.
Roy Thomson Hall, Toronto's premier concert hall, is named in his honour.