"Canadian truckers rule," Musk wrote to his nearly 72 million followers, adding "CB radios are free from govt/media control."
Later he added another tweet that said, "If you scare people enough, they will demand removal of freedom. This is the path to tyranny."
Anti-vaccine mandate truckers in Ottowa have participated in a protest convoy demonstrating against the Jan. 15 mandate for cross-border drivers.
The Freedom Convoy left from Vancouver for Ottawa on Sunday.
Musk told Time last month in an interview after he was selected a "Person of the Year" that he and his eligible children are all vaccinated because the science is "unequivocal" but said he is opposed to mandates.
The unvaccinated are "taking a risk, but people do risky things all the time," he told Time. "I believe we've got to watch out for the erosion of freedom in America."
In the past, Musk had questioned the vaccine and downplayed the pandemic. He also defied California’s 2020 stay-at-home order to keep Tesla factories open, eventually opting to move to Texas.
The Canadian Trucking Alliance estimates that roughly 15% of truckers in the country are not fully vaccinated, or about 16,000 truck drivers.
Fox News' Emma Colton contributed to this report.