The information came to light from documents obtained by the BBC and Buzzfeed, revealing the syndicates profited from bets on matches thought to have been fixed, including three at Wimbledon.
Betting syndicates from Russia were also allegedly involved in the scandal, the BBC said.
The investigation dated back over the last decade, with 16 players ranked in the world's top 50 suspected of being involved in the match-rigging.
The 16 were repeatedly flagged to the Tennis Integrity Unit (TIU), which was set up to police the sport, but all were allowed to continue playing, the BBC said.
A report in La Stampa suggested the Italian betting syndicates were mafia-linked. A confidential report to tennis authorities in 2008 said some 28 players were involved in matches linked to the Italian and Russian betting syndicates, but the findings were allegedly never pursued.
A group of 10 players were “pulling the strings” for the networks, the BBC reported.
Chris Kemode, head of the Association of Tennis Professionals (ATP), the governing body of men's professional tennis, refuted claims that match-fixing was covered up or not properly investigated.
"While the BBC and BuzzFeed reports mainly refer to events from about 10 years ago, we will investigate any new information," he was quoted by the BBC as saying.