Giulio Perrone, who is in his mid-sixties, had been a fugitive since 1998, when his lawyers failed in a final appeal against a 22-year prison sentence for links to the Naples mafia, the Camorra, and international drug trafficking.
He was first charged in 1993 after he and his wife were arrested while trying to import 16 kilos (35 pounds) of cocaine.
Perrone disappeared the following year and had been unheard of until Italian police established, through Facebook, that he was living as Saverio Garcia Galiero, in Tampico, in the state of Tamaulipas in Mexico.
The police did not reveal details of how they traced him through the social media site.
Under the extensive powers Italian investigators enjoy when involved in anti-mafia cases, they could have been monitoring the online activity of associates of Perrone in Italy.
Or they may have come across a picture of him by using image-recognition software, which is an increasingly useful tool for detectives tracking fugitives.
Perrone, who had remarried and had Mexican children, was described by police as a prominent figure in Italy's drug trade in the 1980s and early 1990s, acting as a wholesale supplier to Camorra clans.
He was arrested earlier this month at his Mexican home and deported, arriving late Friday in Rome.