The ever popular second row admits the club has changed beyond all recognition during his time at Sixways and he is enjoying his rugby more than ever now under the guidance of Director of Rugby Mike Ruddock.
And he revealed the club's big plans for the future had made his decision to extend his stay a simple one.
"I'm delighted to sign a new contract and commit my future, having already had six enjoyable years at Warriors," said Gillies.
"I'm still very motivated by the club and what we are striving trying to achieve. There are a lot of exciting plans, both on and off the field, and I want to be a part of that development.
"The squad is the strongest that I've been involved in since I was at Warriors and we are looking to play an exciting brand of rugby that is good to watch and be a part of. We also have a very close knit group of players and I've built up some very strong friendships over the past six years.
"The club boasts a fantastic coaching set-up with Mike Ruddock, Clive Griffiths and Billy McGinty plus a dedicated backroom team who are all working hard for success and to ensure they create a positive environment to be a part of.
"Warriors are also fortunate to have such a passionate chairman as Cecil Duckworth, whose vision and investment has given the club such a fantastic backing, and superb supporters who have always stood by me and the team. I look forward to being part of a side that can make them proud in the coming years."