The 27-year-old, who joined from London Welsh in 2011, has scored 12 tries in 18 appearances for Worcester this season.
Worcester head coach Richard Hill told the club's official website: "Josh came to Warriors as a very raw player with a huge amount of ability and natural talent, particularly in attack.
"His game needed refining to become a top Aviva Premiership player and, credit to him, he has worked exceptionally hard during his time here.
"Josh has become a very good defender and has filled some big boots since the departure of Miles Benjamin and Marcel Garvey last year."
Hill added that Drauniniu has "realised" his potential.
"In attack he is now even more hungry for the ball and is a real predator," said Hill. "I think he has finally realised just how good a player he can be and I rate him as one of the best attacking wingers and in the top three in the country.
"He has got it all and he plays with a smile on his face, which I like to see. Josh has a very big future and we are delighted that is with Worcester Warriors."
Drauniniu is a former England sevens international.