A New York jury found that Mark Scott helped to perpetrate the scheme, routing approximately $400m (£310m) out of the US while working to conceal the true ownership and source of the funds.
Prosecutors said he made about $50m.
Mr Scott's lawyers had said he did not know that OneCoin was worthless.
They said he was simply doing the job asked by Dr Ruja Ignatova, a co-founder of the Bulgaria-based OneCoin.
The federal jury in Manhattan rejected those arguments, finding Mr Scott guilty of conspiracy to commit money laundering and bank fraud.
Dr Ignatova's brother, who testified in the case, also recently pleaded guilty for his role in the fraud.
US-based investors claiming to have been defrauded by the scheme are also attempting to sue Mr Scott for recompense in a related case.