The 29-year-old had been in talks with the Cottagers in January, and while a deal had been struck, red tape had prevented the deal going through. Boateng has been at the Africa Cup of Nations with Ghana - but had hoped the move would go through during his spell at the tournament in South Africa.
Boateng has been playing for Dnipro in Ukraine, but he has been in dispute and had looked to take his case to the Court of Arbitration for Sport to try and secure his release from his contract. However, with the Fulham deal faltering, Olympiakos have now stepped in and are looking to push through a move.
It is understood that Boateng is now in Greece undergoing a medical with the Athens outfit.