He racked up 41 RaboDirect PRO12 appearances for the region, including seven appearances this season, but has not featured in the league since January.
He will join up with former teammate Ben Morgan, who also made the switch to Kingsholm last season, and admitted he was grateful for all the support he had received from the Scarlets during his time with the region.
He said: "I'm extremely honoured and excited to sign for Gloucester for a whole host of reasons, but not least the passionate supporters, the quality of the playing squad, the famous history of the club and because of Nigel Davies who was my coach at the Scarlets.
"I would like to thank the Scarlets and their supporters for the support I received whilst at the club, but I now look forward to my immediate future at Kingsholm."
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