His lawyer Blair Suffredine has already said Blackmore would challenge the constitutionality of Canada's polygamy laws if his client was found guilty.
"I'm guilty of living my religion and that's all I'm saying today because I've never denied that," Blackmore told reporters after the verdict.
"Twenty-seven years and tens of millions of dollars later, all we've proved is something we've never denied. I've never denied my faith. This is what we expected," he added.
Under Canadian law the maximum penalty each man will face is five years in prison; both men will be sentenced at future hearings.
Both Blackmore and Oler are members of the Fundamentalist Church of Jesus Christ of Latter-Day Saints, which is a breakaway Mormon sect that believes in plural marriage.
The mainstream Mormon Church renounced polygamy in the late 19th century and disputes any connection to the fundamentalist group's form of Mormonism.
The trial of the men lasted for 12 days and included mainstream Mormon experts and law enforcement officials, as well as Jane Blackmore, a former wife of Winston's who left the community in 2003.
Madam Justice Sheri Ann Donegan said Jane Blackmore was a credible witness.
From @CdnPressVideo: Winston Blackmore not surprised by guilty verdict for polygamy https://t.co/km9BgXjIgT pic.twitter.com/r7kxwDGcUX
— The Canadian Press (@CdnPress) 25 July 2017
"She was a careful witness," Madam Justice Donegan said.
"There was nothing contrived or rehearsed in her answers. She was impartial," she added.
Much of the evidence in the trial came from marriage and personal records seized by law enforcement at a church compound in Texas in 2008.
