Former bankers Frederic Marino and Yoshiki Ohmura, accused of conspiring to commit fraud between 2009 and 2014, were found guilty by a jury at London's Southwark Crown Court after a trial that lasted eight weeks.
A former employee of JP Morgan Chase, Mr Marino had a role in setting up asset management company FM Capital Partners to manage money invested from the Libya Africa Investment Portfolio. Meanwhile, Mr Ohmura, who used to work for the bank Julius Baer, had acted as a mediator to FMCP.
The pair arranged for fees from the funds to be paid offshore, while they channelled what prosecutors called "secret profits" to a company, after taking a cut.
The payments, which were worth more than $15.3 million, involved 17 investments made by the Libyan fund to four investment banks between 2009 and 2011.
Some of the money siphoned off was used to pay those who were aware of the scheme and demanded "hush money". All of it was done without the knowledge of the fund.
A third banker, Aurelien Bessot, a director of FM Capital Partners, had previously pleaded guilty.
Sentencing will take place in February and Judge Tony Baumgartner said a jail term was “almost inevitable”. Mr Marino never attended the trail.
Lawyers for Ohmura and Marino did not immediately respond to a request for comment.