US authorities describe the case as the largest ever international money laundering prosecution which targeted a Costa Rica-based digital currency operator.
Vladimir Kats, 41, who was arrested in May and originally pled not guilty, reversed his plea before US District Judge Denise Cote.
He confessed to money laundering and operating an unlicensed money transmitting business.
Kats allegedly helped set up and run Liberty Reserve, which handled huge amounts of money outside the control of governments and is charged with running a $6 billion money laundering racket between 2006 and 2013.
Six other people who worked at Liberty Reserve are also been charged with conspiracy to commit money laundering, conspiracy to operate an unlicensed money transmitting business, and operation of an unlicensed money transmitting business.
Kats, a US citizen, is also accused of receiving and distributing child pornography and of having a sham wedding in 2002 to help his bride fraudulently obtain US citizenship.
Manhattan US Attorney Preet Bharara welcomed his plea.
“With his guilty plea today, we take a significant step toward punishing those responsible for creating and running this international den of cybercrime,” he said.
Five of the seven were arrested in May in Costa Rica, Spain and New York, sealing the fate of a company that had been one of the most successful in the popular but increasingly scrutinized world of unofficial banking and virtual currencies.
The other two suspects remain at large.
The probe involved law enforcement in 17 countries and “is believed to be the largest money laundering prosecution in history,” prosecutors have said.
Authorities say that when Liberty Reserve realized it was under investigation, it made a show of shutting down, yet continued to operate behind an array of shell companies in Australia, China, Cyprus, Hong Kong, Morocco, Russia and Spain.
Editor’s Note: Inside Costa Rica covered extensively the case of Liberty Reserve earlier this year. Our previous coverage can be found here.