Hobbs made his debut for the Blues in 2009 and has made 11 appearances this GUINNESS PRO12 season, scoring one try.
But he is now looking forward to beginning the new chapter in his career.
"I am really looking forward to the new challenge ahead at Newport Gwent Dragons," said Hobbs, who was named in Wales' training squad for the summer tour of Japan in 2013.
"There are good people here, good coaches and a strong squad along with some great training facilities and a fantastic support base.
"I would like to thank everyone at Cardiff Blues for the continued support they have given me throughout the years I have been with the region."
Hobbs will battle for the No.1 jersey with in-form Phil Price and up-and-comer Luke Garrett next season, with the experienced Boris Stankovich's contract expiring at the end of the campaign.
Director of rugby Lyn Jones added: "I have always been impressed with Sam as an all-round player.
"When we were made aware of his availability we had no hesitation in making him an offer to stay in Wales, beating off offers from England.
"He will add a great deal of experience and character to a maturing Newport Gwent Dragons squad."
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