Second row forward Sidoli (29), who has won 42 Welsh caps, made his international debut against South Africa in 2002 and started every match in Wales' 2005 Grand Slam. He has packed down with Luke Charteris in three international games already and will provide the Dragons with a solid and seasoned second row combination.
"I'm glad to have the opportunity to come home to Wales," said Sidoli. "I know Luke Charteris well from our time together with the Welsh squad and I'm looking forward to playing alongside him. I already know a good number of the players here but I'm keen to meet those I don't. The Dragons have a lot of exciting young talent and it's going to be great to be part of this team.
"It was hard to leave Bristol, they are a good bunch of guys and I enjoyed the set-up there, but the Dragons offer a high level of rugby and I'm looking forward to getting on with pre-season training and fronting up for the first game of the season."
Dragons Rugby Manager Robert Beale said "We are delighted to bring Rob to Rodney Parade. He has a wealth of experience playing in the second row and he will definitely add to what is already impressive group of second rows at the region.
"When Rob became available, there was really no question about whether to bring him to Rodney Parade. Part of the region's three-year plan is to Welsh players to our region and to be able to bring back a quality Welsh player like Rob was a great opportunity.
"The knowledge gained by Rob and Luke Charteris playing in the national team will give a great opportunity for our younger players to gain from their combined experience.
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