The 18-year-old came on with just five minutes of the game left to play, and with the Gunners 1-0 behind.
Josh Murphy had given the Canaries the lead with a first-half strike, but a Nketiah toe-poke from a corner took the game to extra time.
The teenager then bagged a header past Angus Gunn to book Arsenal’s place in the quarter-finals of the competition.
Here’s how our man Adrian Kajumba rated the performances from the Emirates.
Was exposed for goal but helped keep Arsenal in tie with saves from Oliveira and Murphy.
Played scorer Murphy onside and didn’t have pace to catch him.
Lucky to escape a red for bringing down Oliveira as last man.
Wasn’t overworked and went close to scoring with first-half header.
Pushed back by Murphy but positive every time he went forward.
Coquelin BOOKED 5
Made little impact on the game other than being booked for rash foul.
Wilshere BOOKED 6
Back in central midfield. Has looked better further forward this season.
Passed up two good opportunities to shoot when he chose to pass instead.
Captain for the night but failed to lead by example.
Was robbed of possession just before the goal. Not his night.
Another ineffective display, this time not rescued by a wonder goal.
Akpom (for Maitland-Niles 70) 6
Nketiah (for Nelson 85) MOTM 9