The 24-year-old has boosted the club's midfield resources and has so far made three appearances for Warriors.
Fatiaki, who made his debut for Fiji off the bench against Japan in 2009, is regarded as one of the most exciting talents in Fijian rugby having already won eight caps, scoring his first-ever try for his country last July against Samoa in Suva.
Head Coach Richard Hill said: "We can see real fantastic potential in Ravai. He is a very bright and has picked up what has been asked of him since he arrived at Sixways exceptionally quickly.
"Ravai is a big powerful man who could be used to carry ball across the game line, but he has also got good hands and an intelligent rugby brain. He can also play both 12 and 13 which is an advantage.
"It is difficult to understate just what a change in lifestyle he has had to overcome since coming over from Fiji and how difficult that can be when you come into a new culture," added Hill.
"He has come from the other side of the world and had to deal with many new things, including playing in snow for the first time last weekend! But he has settled in very well and he will continue to do so for the rest of this season.
"We can see more than enough in Ravai to know he will be a big asset for the Warriors when he has got used to his new life here. He has fantastic potential to get even better and we know he will be a really good player for us in the future."
Fatiaki was delighted to secure his future and added: "I have really enjoyed my time already in England in Worcester and with the team at Warriors who have all helped me settle into a new country.
"I feel my game can only get better here with the coaching team and playing in the Aviva Premiership. I look forward to the coming years as a Warrior and hope we can all bring success to Sixways."