The Wales back-row, set to line up at number No. 8 in next week's Six Nations opener at home to Scotland, has agreed what the Newport-based Dragons said was "a multi-year" deal.
The forward would have been on the radar of several clubs after impressing for Wales at last year's World Cup in France, while fellow international Louis Rees-Zammit has quit the sport completely to try his hand at American Football.
But Wainwright, capped 43 times by Wales, said Friday: "I am looking forward to the next few years. I love the Dragons, I am a home boy.
"I love turning up to Rodney Parade, seeing fans out on the terraces, and that's what I want to keep doing, turning up on a Friday, Saturday or Sunday and playing well, trying to make them happy."
Wainwright, who made his Wales debut in 2018, is set to become an increasingly influential figure this Six Nations given fellow loose forwards Taulupe Faletau and Jac Morgan are both set to miss the whole Championship through injury.
He could now move from blindside flanker, unless Wales coach Warren Gatland decides to give Cardiff No. 8 Mackenzie Martin a debut and leave Wainwright in the No. 6 jersey.
Scotland have not beaten Wales in Cardiff since 2002 - when current head coach Gregor Townsend was their fly-half - in a run of 11 successive Test defeats in the Welsh capital.