Trudeau is currently in prison on contempt of court charges. A jury found him guilty in November for violating an agreement about deceptive infomercials related to his weight-loss book.
The judge didn't believe Trudeau and sent him back to prison. Trudeau will be sentenced in March.
Trudeau was taken into custody right after the verdict after the judge deemed him a flight risk. He now faces the possibility of years in prison.
"We're disappointed in the verdict. We had hoped it would come out the other way," said Thomas Kirsch, Trudeau's attorney.
There were hugs and tears from the crowd of supporters who attended his trial daily.
"There's thousands of people around the world whose lives are changing because of him, whether he's locked up or not. And I think that speaks volumes," said Jumal Lewis, Trudeau supporter.