Former construction boss Tony Accurso will have to surrender to prison authorities to serve a four-year sentence.
In a 76-page judgment, Quebec's Court of Appeal upheld his 2018 conviction for colluding over public contracts in Laval.
Accurso, who had appealed that guilty verdict and sentence, has until Wednesday, June 1 to report to prison.
The path to this conviction has been complicated.
In November 2017, Judge James Brunton declared a mistrial when a member of the jury admitted to having received information that had not been revealed during the trial.
In a 2018 retrial, Accurso was found guilty on all five counts: conspiracy to commit acts of corruption, conspiracy to commit fraud, fraud of over $5,000, municipal corruption and aiding in a breach of trust.
Accurso spent a few days behind bars, before being released on bail when his lawyer appealed the judgment.
One of the arguments his defence invoked before Quebec's Court of Appeal is that the 2017 mistrial had allowed the prosecution to improve its evidence for the second trial, rendering it unfair.
Accurso's lawyers argued that the province's anti-corruption squad (UPAC) investigation into the circumstances surrounding the jury's tainting had enabled the prosecution to obtain privileged information. In particular, the defence said the prosecution could have gained insight into the jury's perception of the first trial, allowing it to adjust during the second trial.
However, Quebec Court of Appeal rejected this argument, finding that Crown prosecutors had not benefited from confidential information.
Laval Mayor Daniel Boyer welcomed the court's decision.
"It's an important reminder to organized crime that their wrongful actions will have consequences," he said in a statement. "After all the work we have done over the past few years, I am convinced that many Laval families have breathed a real sigh of relief."
"We can assure them that we will continue the work and that we will not let our guard down."
Accurso's lawyer, Marc Labelle, could apply to the Supreme Court of Canada for leave to appeal.