An accountant pleaded guilty in federal court to charges he helped a client evade U.S. taxes in a case stemming from a trove of leaked documents known as the Panama Papers.

Richard Gaffey, a Massachusetts resident, had been scheduled to go to trial March 6. Instead, he pleaded guilty Friday to an eight-count indictment that charged him with wire fraud, conspiracy to commit money laundering and conspiracy to defraud the Internal Revenue Service, among other charges.

A lawyer for Mr. Gaffey didn’t return a request for comment. He is scheduled to be sentenced June 29.

Mr. Gaffey helped clients evade U.S. taxes, including by obscuring their ownership of offshore shell companies and bank accounts holding tens of millions of dollars in investments, prosecutors said.

His guilty plea follows that of another defendant in the case, Harald von der Goltz, a former U.S. resident and one of the accountant’s former clients. Lawyers for Mr. von der Goltz didn’t immediately return a request for comment.

Messrs. Gaffey and von der Goltz were charged as part of a federal investigation sparked by the internal files of the Panama-based law firm Mossack Fonseca. The documents, which were published by a consortium of journalists in 2016, revealed that the firm had created hundreds of thousands of shell companies and offshore accounts for clients around the world.

The U.S. Justice Department also charged two former employees of now-defunct Mossack Fonseca and an associated investment firm as part of the investigation.

Prosecutors last year said Dirk Brauer, a German citizen, had been extradited to Germany to face criminal charges there. Ramses Owens, a Panamanian citizen and a former Mossack Fonseca partner, faces criminal charges in Panama.

Lawyers for both defendants didn’t return requests for comment.