The world governing body of gymnastics says Cory Marsh failed a drug test at the acrobatic world junior championships in Orlando in April.
The 18-year from Oakville, Ont., finished 11th in the men's pairs event with teammate Jamie Patrick. That result has been negated as a result of the drug test.
Marsh is not eligible to compete again until Nov. 22. He was also fined US$1,000.
He has 21 days to appeal.
Philippe Silacci, media officer for the Federation Internationale de Gymnastique, says there has only been a handful of positive tests for marijuana in his sport over the last 20 years.
The federation recently went to the Court of Arbitration for Sport to contest the World Anti-Doping Agency's contention that a test for marijuana required a two-year ban from competition.
The federation successfully argued in the case of a Russian athlete that marijuana was not performance-enhancing in the sport and that a two-year suspension was overly harsh.