Berry, 27, joined Wasps two seasons ago from Racing Metro and had made 40 appearances to date.
With Joe Simpson ruled out through injury, Berry will play an increasingly important role in the season run-in.
The Australian said: "I am delighted to have renewed my contract with Wasps. Though we've had a tough season so far I totally believe we have the coaching staff and players to restore the club to where it should be.
"Both my wife and I have made some great friends through the club and we are excited to be extending our stay here in London."
Director of rugby at Wasps Dai Young added: "I have been really impressed with Nic this season. He is a talented number nine with a great attitude and I'm delighted that he's staying here.
"We've got a pool of very good scrum-halves in places for next season and that competition for places is extremely healthy."
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