The 25-year-old, who is Exeter's first signing for the new season, has put pen to paper on a two-year deal.
"Obviously we are delighted to have got Tom on board," Exeter head coach Rob Baxter told the club's official website. "We've had a good look at Tom over a period of time and for us it's difficult to ignore proven try-scorers who have got a very good ability to break the gain line."
James added: "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."
James heads to Sandy Park with 10 caps for Wales under his belt.