Media tycoon Conrad Black has been convicted of three charges of fraud and one of obstructing justice.
Black, 62, was cleared of racketeering and tax evasion but could face 35 years in jail when sentenced on 30 November. His lawyers said he would appeal.
He was facing 13 charges over claims he stole $60m (£29.5m) from investors in newspaper firm Hollinger International, which used to own the Daily Telegraph.
The Chicago jury also convicted three of the UK peer's associates of fraud.
Judge Amy St Eve adjourned Black's bail proceedings until Thursday to allow his defence team to consult Canadian lawyers. Black was allowed to remain free on a $21m bond.
He also handed over his UK passport to the court and will remain in the Chicago area until next week.
He had given up his Canadian citizenship in 2000 to become a British lord, after a court decision in his home country to block his acceptance of a peerage.
The guilty verdicts cap a remarkable fall from grace for Black, once one of the UK's wealthiest and most influential media figures.
The jury of nine women and three men took 12 days to reach a verdict in the high-profile case, after initially telling the judge that they could not reach an unanimous judgment.
Black, who remained impassive as the verdicts were read out, was found guilty of taking money owed to investors in the form of "non-compete" payments originating from the sale of newspaper titles.
But he was cleared of abusing company resources to fund his extravagant lifestyle.
Three of Black's associates - Jack Boultbee, Peter Atkinson and Mark Kipnis - were also found guilty of fraud at the end of the 16-week trial.
Black was present in court to hear the verdict along with his wife, Barbara Amiel Black.
The charges on which he was found guilty carry a maximum penalty of 35 years in prison.
'Lengthy prison sentence'
After the hearing his lawyer, Edward Greenspan, said: "We intend to appeal and there are viable legal issues. We vehemently disagree with the government's position on sentencing.
"We believe, based on the conviction of the charges here, that the sentences for this type of offence are far less than what the government suggested."
Black ran one of the largest newspaper groups in the world
Legal experts said that although he had been cleared on several charges, the convictions for fraud were damning.
"It only takes one fraud charge and the man is disgraced and finished," said Joshua Rozenberg, legal editor of the Daily Telegraph.
"He is clearly facing a lengthy prison sentence."
David Radler, the British peer's former second-in-command at Hollinger, testified against Black after himself admitting fraud in return for a reduced sentence.
Radler told the court Black had personally initiated a fraudulent scheme to pocket payments which rival firms had agreed to pay Hollinger to limit competition in key markets.
Black's lawyers argued that Radler was a "self-confessed liar" and that the payments had been authorised by the company.
Hollinger's newspaper empire once spanned the globe, including titles such as the National Post of Canada and the Jerusalem Post.