The construction wing of the Quebec Federation of Labour has confirmed Bernard (Rambo) Gauthier's conviction today at a courthouse in Sept-Iles.
It says he was acquitted on a charge of harassment.
The intimidation conviction is related to an incident involving contractor Frederic Boucher during a strike in the construction industry in June 2013.
At the time union members were visiting construction sites to ensure the strike mandate was being respected.
Gauthier testified last February at the Charbonneau Commission looking into corruption in the construction industry and denied using intimidation on sites.
Sentencing arguments have been set for Feb. 3.
The construction wing said it is studying the file to determine whether it should appeal the decision.
Gauthier told the Charbonneau Commission his main goal as a union boss was to ensure his workers were all able to have a job.
His name had come up in previous testimony as the commission heard about threats and extortion on the province's North Shore.
The heavy-machinery operator was described as a controlling figure who was not above advocating violence and intimidation to ensure local workers were hired.
A corruption inquiry investigator described the North Shore region as a state within a state, with Gauthier and his lieutenants using intimidation and thuggery to maintain control.
Gauthier disputed some of those allegations, telling the inquiry that work was hard to find in the far-flung region and that if collective agreements were strictly adhered to, it was to ensure everyone had access to work.
The former Canadian Forces member also explained that his memorable nickname was not linked to his military service.
He said he came by it because he would spy on security at one of his first jobs in the early 1990s.
Gauthier said the "Rambo'' name was amplified by the media and that most people simply knew him as Bernard or "Ti-Ben.''