The fans chanted and lit flares as the new new signing made his way onto the field at Georgios Karaiskakis Stadium in the port of Piraeus.
Real Madrid great Marcelo welcomed by 20,000 Olympiacos fans in Greece.
Marcelo, accompanied by his family, arrived at Athens International Airport in the afternoon by private jet and was taken to the stadium by club sports director Christian Karembeu.
He entered the field wearing the same No.12 he wore at Real Madrid for the past 16 seasons.
"Thank you. I am very happy and satisfied. My family too. I hope to help the team with great devotion," Marcelo told the fans, adding in Greek, "Let's go, Olympiakos!"