Johnson has been with the Canaries since July 2011 when he completed a Bosman free transfer from Leeds United and he has made 57 appearances since, scoring three goals.
He has only missed one Premier League game this season and admitted he was delighted to sign a new deal with the club.
"As soon as I heard that the club wanted to sit down and sort a new deal I just wanted to get it done and I'm delighted that it has," Johnson said.
"I think I'm playing the best football of my career and I'm playing in the best league in the world.
"I think this is a club that is moving forward and I want to be a part of that. We've proved that we're good enough to be here and we know how hard it is to stay in this league, but we work as hard as we can to do exactly that.
"It's been a good month for me. I had the arrival of my baby boy three weeks ago and now I've signed a new contract."
Boss Chris Hughton said: "I'm absolutely delighted we have secured the services of Bradley Johnson. He has been a tremendously consistent performer for us in midfield not just this season, but since he joined the club from Leeds United."