Matavesi, who previously played for Exeter Chiefs until his move to the Top 14 in 2011, will move to Sixways from the start of next season following the completion of talks.
The Cornwall-born 21-year-old, who can play across the back line and has featured regularly at inside centre for Racing Metro, has already earned five international caps for his country scoring 12 points with the boot.
Head Coach Richard Hill said: "We are very pleased that we can confirm the news that Josh will be joining the Warriors.
"We needed two good strong inside centres now we have released Dale Rasmussen and Sione Tu'ipulotu. Ravai Fatiaki has been fantastic the last six months with us and has really good potential. When you add that to the signing of Josh, we are pleased with our midfield options.
"Josh is a player we've been watching closely and he excites us with the way he plays. We already have some players within our squad who know him well from his Exeter days and Cornish connections.
"He has had a great experience at Racing Metro, where he has played Heineken Cup rugby, and he is excited about his move to Sixways. He is somebody who is an attacking player, who plays with flair and will look to unlock defences, which is what we need to add to our game.
"Josh takes ball to the line, is good at offloading out of contact and as a Fijian he loves to tackle hard. Phil Larder is looking forward to working with him and integrating him into our systems.
"Josh also gives us a kicking option in midfield or if he operates at full back or fly half. He gives us plenty of options and we are excited about the prospect of seeing him in action for the Warriors."
Matavesi added: "I'm very pleased to be coming back to the Aviva Premiership and show how much I have improved as a player. This is a big opportunity for me at Sixways and one I plan to take with both hands."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The Barbarians are one of the top invitational rugby sides with a long history and classic rugby jersey.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Lions get ready for their matches with this green training jersey. It's what the players wear. Get in the Gear!
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The Lions are ready to get their Australia tour underway. They arrive in Perth on Monday.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.