Rising star Fatiaki, who has been playing his rugby in Tailevu in Fiji, recently featured in the Pacific Nations Cup and scored his first-ever try for Fiji earlier this month against Samoa in Suva.
The 24-year-old, who made his debut for Fiji off the bench against Japan in 2009, also started at inside centre against the mighty All Blacks in Dunedin earlier today (Friday).
Fatiaki, who is 6ft and weighs 16st 1lb, is regarded as one of the most exciting talents in Fijian rugby and is expected to join up with Warriors after the completion of the Rugby World Cup in New Zealand.
Head Coach Richard Hill said: "We have been looking for a player to bolster our midfield selection options this coming season and so we are pleased to announce that Ravai will now join us.
"He is rated as one of the rising stars of Fijian rugby and I have spoken at length to national coach Greg Mumm about him. Ravai is a powerful ball carrier who is very coachable and eager and keen to learn.
"Ravai is similar in many ways to a number of the Fijians who have been playing in France, like Gabriele Lovobalavu at Toulon and Seru Rabeni at La Rochelle.
"I also recently watched him play for Fiji as they beat Samoa where he really came into his own in the second half and capped a fine display with a try.
"We are always on the lookout for players that have the potential to be very good and can adapt to play the style in which I want the Warriors to play. This is a fantastic opportunity for Ravai to come over to England and develop his game at Sixways while experiencing a new culture and lifestyle."
Fatiaki said: "I look forward to having a chance to play in a great competition like the Aviva Premiership. I've heard plenty of good things about Worcester and I know they're an ambitious club. It's a big opportunity and I'll certainly be giving it my best.
"My focus at the moment is making the Fijian team to play in the Rugby World Cup. We hada big gamethis Friday against the All Blacks, which wasa real challenge, and we've had some strong preparation including the Pacific Nations Cup, so hopefully we'll do well."