Julius Thomson was a member of the Toronto Argonauts Rowing Club when he was selected to represent Canada in the coxed eights at the 1908 Summer Olympics. There, alongside Gordon Balfour, Becher Gale, Douglas Kertland, Walter Lewis, Charles Riddy, Irvine Robertson, Geoffrey Taylor, and Joe Wright, Sr., he was defeated in the semifinals by the eventual gold medal-winning Leander crew from Great Britain and settled for bronze. Thomson was in the insurance business and, early in his career, worked for the Ontario Accident Insurance Company.