Bradley Johnson joined Derby from Norwich in September 2015
Bradley Johnson condemned his former club Norwich to a fifth successive loss as Derby sealed a fourth straight win.
Johnson struck midway through the second half when his low shot from 25 yards found the bottom corner.
John Ruddy denied Johnson and Jacob Butterfield as Derby improved after a quiet first half.
Steven Naismith had City's best chance when he forced Scott Carson to save, but the Rams kept a fifth straight clean sheet at the iPro Stadium.
Norwich bossed much of the first half, with Wes Hoolahan influential, but failed to register a shot on target against the second-meanest defence in the Championship.
Alex Neil's side, who had a penalty claim waved away when Jacob Murphy went down during a late spell of pressure, drop to seventh after a fourth defeat in six away matches.
Derby have won five of seven matches since Steve McClaren's return as manager and move up to eighth, just two points outside the play-off positions.
Derby manager Steve McClaren said:
"It's a big win for us; a big step forward. We had to dig in at times, but that's a good team we've kept a clean sheet against.
"We controlled the game when we had the ball or didn't have the ball and that's important if you want to be a top team.
"We might lose next week, but I know this team is capable of winning big games and today went a long way to showing me this team has got something."
Norwich manager Alex Neil:
"I've just seen the owner (Delia Smith) and she literally said to me, 'Keep going, we keep fighting'.
"She and Jez Moxey (chief executive) come down regularly after games and they know how hard I'm trying and how hard the players are trying.
"All you can do is stick together and keep together and we'll get through it. The one thing I have never been is someone who is going to give up. I think you only ever fail when you stop trying."
