The body of Marcello Putzu, who would have been 59 this year, was found only because a neighbour in the San Gavino Monreale area of Cagliari reported a leak coming from the apartment.
Firefighters had to break down the door of the home, which neighbours believed had simply been vacated by the previous dwellers, before discovering the man's skeleton, Unione Sarda reported.
Nobody had questioned Putzo's disappearance, and nobody went looking for him, the newspaper said.
Some receipts and prescriptions, dating back to 2011, along with some food, were found in the apartment.
Putzo, a father of two, was made redundant from his role as a train technician, and never found a job again, the newspaper said. His wife left with their two young children in 2007.
He is believed to have died of natural causes.