The 25-year-old has decided on a switch to the Aviva Premiership after spending seven years with Cardiff Blues.
James has made 10 appearances for Wales as well as over 100 league and cup appearances for the Blues, for whom he has scored 39 tries.
He told Exeter's official website: "Signing for Exeter Chiefs is a great move for me. They are a team that I've watched come up to the Premiership over the last few years and do really well.
"I've had a fantastic seven years with the Blues and I am very grateful to have been given the opportunity to play for them and for the support I've been shown over my career. But I felt the time was right for a fresh challenge.
"Exeter are clearly an ambitious club and having talked to the coaches about where they want to go and also the plans for the stadium, I felt I wanted to be a part of it all and experience something different."
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