Michael Avenatti has been found guilty of defrauding Stormy Daniels of nearly $300,000 (£221,000) in a Manhattan federal court.
Avenatti, 50, stared straight ahead as the jury returned guilty verdicts on wire fraud and aggravated identity theft charges.
He now faces up to 20 years in prison for stealing part of an $800,000 (£590,000) advance Ms Daniels was owed for her 2018 autobiography Full Disclosure, and forging her signature in a contract.
Outside court, Avenatti said he was “very disappointed in the jury’s verdict”.
“I’m looking forward to a full adjudication of all the issues on appeal.”
Judge Jesse Furman ordered Avenatti to surrender to US Marshalls in California on Monday.
Avenatti has delayed beginning a 2.5 year prison sentence for his 2020 conviction in an extortion case while waiting for the book proceeds trial and the retrial of a fraud case in a California federal court.
Prosecutors said it was likely Ms Daniels would speak at his sentencing on 24 May.
In a statement released shortly after the verdicts, Ms Daniels’s lawyer Clark Brewster said she was “relieved this nightmare is over”.
“The text communications between Stormy and Mr Avenatti in real time was overwhelming proof of his receipt and embezzlement.
“The forgery of her name and his concealed directive to wire the money to him was irrefutable.
“Still, Mr Avenatti possessed the uncanny ability to steadfastly deny the crimes and persuade others he was entitled to the embezzled funds.
“Stormy is pleased that the justice system works.”
The jury reached a verdict just before 1500 local time [2000 GMT] on Friday after more than a day of deliberations.
Earlier, they returned a note suggesting that one female juror had been holding out, and that she was refusing to deliberate with other panellists.
During the two-week trial, prosecutors said the California lawyer cheated Ms Daniels of nearly $300,000 she was owed for her autobiography, spending it on his firm’s payroll and personal expenses.
Avenatti argued that he was owed the money and never thought it was wrong to take it.
After firing his public defenders on day two of the trial, he cross-examined Ms Daniels about her ability to speak to dead people and “dark entities that prowled” her former New Orleans home as he attempted to shatter her credibility.
In a tweet after the verdicts were reached, former Trump lawyer Michael Cohen said: “Justice has been served. Michael Avenatti has shown himself to be what I have always known him to be… a conman, a liar and a thief.”
Avenatti helped secure the book deal for Ms Daniels in spring 2018, shortly after he began representing her in lawsuits meant to free her from the rules of a 2016 payment of $130,000 she had received from President Donald Trump’s personal lawyer Mr Cohen to remain silent about an alleged affair with Mr Trump a decade before. The hush-money payment occurred just days before Mr Trump was elected president in 2016. He has denied the claims by Ms Daniels.
Mr Avenatti used his heightened profile at the time to make frequent appearances on cable television news programmes.
Ms Daniels, a porn actress who has also earned stage credits in two mainstream movies, testified during the trial that she never authorised Mr Avenatti to pocket some of the $800,000 advance on her autobiography, Full Disclosure, which was published in the fall of 2018.
Associated Press contributed to this report
