Merthyr-born Sidoli, the brother of Wales star Robert, has Italian heritage through his father Primo, who moved to Wales from Bardi at the age of 20.
“To be able to play for a successful Italian side is a dream,” he said. “Growing up as part of a strong Italian family in South Wales, I always hoped that one day I would be able to move to Italy and make a living out of what I love doing.
“I have learnt so much over the last few years with the Dragons under the guidance of Jim McCreedy, so I hope that I can bring what I have learnt to Calvisano as well as learning from my new team.”
Sidoli, 28, has made 114 Dragons appearances since joining from Ebbw Vale and was an uncapped member of Wales’s 2004 summer tour.