Evan Greebel, who was outside counsel to Shkreli's former company Retrophin Inc, was found guilty by a federal jury in Brooklyn of charges he conspired to commit wire fraud and securities fraud, prosecutors said.
"We are shocked by the verdict," said Reed Brodsky, a lawyer for Greebel. "We will continue to fight for justice for Evan Greebel and his family."
Acting U.S. Attorney Bridget Rohde in Brooklyn said the verdict sent a message to lawyers that they will be held accountable when they "use their legal expertise to facilitate the commission of crime."
The verdict came after a different jury in August found Shkreli guilty of defrauding hedge fund investors, but not guilty of conspiring with Greebel to steal from Retrophin. He has denied wrongdoing.
Greebel, 44, was a partner at the law firm Katten Muchin Rosenman when he was working for Retrophin. He later joined the firm Kaye Scholer, but resigned after his arrest in December 2015.
Shkreli, 34, became notorious in 2015 when he raised the price of anti-parasitic drug Daraprim to $750 a pill, from $13.50, as chief executive of Turing Pharmaceuticals. The price hike is unrelated to the criminal case.
The charges he and Greebel faced related to Shkreli's management of his previous drug company, Retrophin, and of two hedge funds, MSMB Capital and MSMB Healthcare, from 2009 to 2014.
Prosecutors have said that Shkreli lied about the funds' finances to lure investors and concealed devastating trading losses. They said he paid investors back with money and shares stolen from Retrophin, which he founded in 2011.
Prosecutors said Greebel assisted Shkreli in defrauding Retrophin through a series of settlement and sham consulting agreements.
In September, following his conviction, Shkreli was jailed after he offered a $5,000 reward in a posting on Facebook for a strand of former presidential candidate Hillary Clinton's hair. That prompted U.S. District Judge Kiyo Matsumoto to revoke his bail.
Greebel denied wrongdoing, and at trial, his lawyers sought to distance their client from Shkreli, whose provocative public behavior earned him the nickname "pharma bro."
Brodsky told jurors during his opening statement that Shkreli lied to Greebel just as he lied to investors.
Greebel was also accused of conspiring with Shkreli to exercise secret control over Retrophin shares belonging to several other shareholders. Shkreli was found guilty of that charge during his trial.
(Reporting by Jan Wolfe and Nate Raymond; Editing by Frances Kerry and Tom Brown)
By Jan Wolfe and Nate Raymond