Bernard (Rambo) Gauthier, who testified at the province's corruption inquiry, will file for appeal on Feb 3, the day of his sentencing hearing.
A Quebec court judge convicted Gauthier last month of intimidating construction entrepreneur Frederic Boucher during a work conflict in 2013.
The Quebec Federation of Labour's construction wing told The Canadian Press on Tuesday that Gauthier's lawyer will seek an absolute discharge, which would allow him to keep his job as a union boss.
The labour group added it will appeal Gauthier's conviction to the Quebec Superior Court on grounds the evidence against him was weak and that the judge erred in concluding the heavy-machine operator threatened a contractor.
Gauthier's name surfaced during Quebec's construction inquiry as the commission heard about threats and extortion on the province's North Shore.
He was described as a controlling figure in the construction industry who was not above advocating violence and intimidation to ensure local workers were hired.
Quebec court Judge Michel Parent concluded that Boucher had grounds to fear for his safety after Gauthier paid him a visit.
Boucher told court Gauthier stood within a few inches of his face and threatened to hit him.
Gauthier denied the claim.
He said he only insulted Boucher and added he was standing a few feet from the entrepreneur, not inches away from his face.
The appeal documents state the witnesses who testified against Gauthier contradicted one another and that the judge was wrong to rule the accused's comments toward Boucher constituted threats against his safety.