The 33-year-old midfielder, who won two Greek league and cup doubles with Olympiacos Piraeus from 2007-2009, has agreed to join Super League team OFI Crete on a one-year deal.
Galletti was diagnosed with severe kidney failure in February 2010, prompting him to retire from football aged 30.
The former Real Zaragoza and Atletico Madrid winger underwent a successful kidney transplant in October 2012, the donor being his father Ruben.
"I'm delighted to have come to Heraklion to play for this club," said Galletti, who was welcomed by thousands of fans at the airport late on Friday.
"I am feeling great and have trained with (Argentine club) Estudiantes. I expect to continue my fitness training here to be ready for the start of the season. I believe I have two to three years of top-level football to offer."
OFI president Manthos Poulinakis said: "We have brought in a top player who will help us both on the pitch and commercially."
Galletti joined Olympiakos in 2007 and quickly became a fan favourite with his creative and direct attacking play. He played 13 times for Argentina, scoring once.