Simon Lappin's first Norwich goal for five years helped Chris Hughton pick up his first win as Canaries manager.
Lappin gave the hosts the lead against Scunthorpe, firing in from 25 yards.
But the League One visitors forced their way back into the League Cup tie when Mark Duffy rifled an equaliser before half-time.
Norwich secured victory when Wes Hoolahan scored from the penalty spot after he had been fouled by Niall Canavan.
It was far from comfortable for Hughton and his players but it was a case of job done for the Premier League club.
The Canaries had managed to establish a level of dominance by the half hour mark and were rewarded with the opening goal in the 32nd minute.
Andrew Surman played a pass in-field to Lappin and he took a touch before rifling a powerful drive past Sam Slocombe in the Scunthorpe goal.
Alan Knill's side have lost all three of their League One games so far this season but they did not let their heads drop and were level two minutes later.
Christian Ribeiro picked out Duffy, who curled in an effort from 30 yards that went in off the inside of the post.
But Norwich advanced to the third round after Hoolahan was brought down in the area by Canavan, the Canaries skipper picking himself up to find the net from the spot in the 56th minute.
Live Text Commentary
Full Time The final whistle goes and the game is over.90:00 +2:26
The ball is swung over by Mark Duffy, Ryan Bennett manages to make a clearance.90:00 +1:15
Outswinging corner taken by Andrew Surman from the left by-line, Shot by Anthony Pilkington. Blocked by Tom Newey.89:47
Free kick awarded for an unfair challenge on Ryan Bennett by Tom Newey. Declan Rudd takes the direct free kick.88:58
The ball is crossed by Christian Ribeiro, clearance by Marc Tierney. Corner taken by Robbie Gibbons, Bobby Grant takes a shot. Blocked by Michael Turner.87:35
The ball is sent over by Christian Ribeiro.87:19
Unfair challenge on David Mirfin by Chris Martin results in a free kick. David Prutton takes the free kick.86:33
Free kick awarded for a foul by Tom Newey on Chris Martin. Direct free kick taken by Ryan Bennett.85:18
The ball is delivered by Chris Martin, David Mirfin manages to make a clearance. Corner taken left-footed by Andrew Surman from the left by-line, Sam Slocombe makes a save.80:46
Foul by Chris Martin on David Mirfin, free kick awarded. Sam Slocombe takes the free kick.79:00 Substitution
Substitution Simeon Jackson joins the action as a substitute, replacing Steve Morison.79:00 Substitution
Substitution Connor Jennings replaces Mike Grella.79:00 Substitution
Substitution Bobby Grant on for Andy Barcham.79:00
The assistant referee flags for offside against Mike Grella. Free kick taken by Ryan Bennett.78:30
The ball is delivered by Jimmy Ryan, Declan Rudd makes a save.77:21
Inswinging corner taken left-footed by Robbie Gibbons, save by Declan Rudd.76:34
Centre by Mark Duffy, David Prutton has a volleyed shot. Save by Declan Rudd. David Prutton decides to take the corner short.74:56
A cross is delivered by Marc Tierney, Andrew Surman takes a shot. Save by Sam Slocombe.74:12
Mike Grella is ruled offside. Indirect free kick taken by Ryan Bennett.73:43
The ball is swung over by Steve Morison, David Mirfin makes a clearance.
George Francomb sends in a cross.70:57
Anthony Pilkington crosses the ball, Niall Canavan manages to make a clearance.69:19
The official flags Mike Grella offside. Declan Rudd restarts play with the free kick.68:56
Shot from 18 yards by Wesley Hoolahan. Save made by Sam Slocombe.68:29
Anthony Pilkington delivers the ball, clearance made by Niall Canavan. The ball is delivered by Anthony Pilkington, clearance made by David Mirfin.65:59 Substitution
Substitution Josh Walker leaves the field to be replaced by David Prutton.65:39
Shot by Josh Walker cleared the net.63:44
Shot by Andy Barcham. Save by Declan Rudd.63:03
Mike Grella takes a shot. Save by Declan Rudd. Corner taken left-footed by Robbie Gibbons from the right by-line, clearance made by Michael Turner.60:31
Michael Turner gives away a free kick for an unfair challenge on Jimmy Ryan. Josh Walker takes the free kick, Robbie Gibbons produces a cross, clearance made by Ryan Bennett.58:53
Robbie Gibbons crosses the ball, Michael Turner makes a clearance.56:50
The ball is delivered by Chris Martin, clearance by Niall Canavan. Corner taken left-footed by Andrew Surman from the right by-line, Niall Canavan manages to make a clearance.56:06
A cross is delivered by Andrew Surman, save by Sam Slocombe.55:07 Goal scored
Goal! - Wesley Hoolahan - Norwich 2 - 1 Scunthorpe Wesley Hoolahan scores a power penalty. Norwich 2-1 Scunthorpe.54:02
Wesley Hoolahan fouled by Niall Canavan, the ref awards a Penalty.51:30 Substitution
Substitution Simon Lappin leaves the field to be replaced by Anthony Pilkington.51:30
The referee blows for offside against Mike Grella. Declan Rudd takes the direct free kick.47:54
Shot by Simon Lappin. David Mirfin gets a block in.45:01
The referee starts the second half.45:00 +3:14 Half time
Half Time It is the end of the first-half.45:00 +2:15
Centre by Wesley Hoolahan. Andrew Surman delivers the ball, Christian Ribeiro makes a clearance. Steve Morison decides to take a short corner.41:12
The ball is crossed by Chris Martin, save by Sam Slocombe.39:08
Andrew Surman takes the inswinging corner, Headed effort from inside the area by Ryan Bennett misses to the left of the target.37:43
The ball is sent over by Christian Ribeiro.36:07
Foul by Robbie Gibbons on Simon Lappin, free kick awarded. Marc Tierney takes the free kick.33:48
Christian Ribeiro provided the assist for the goal.33:48 Goal scored
Goal! - Mark Duffy - Norwich 1 - 1 Scunthorpe Mark Duffy scores a goal from long range to the top right corner of the goal. Norwich 1-1 Scunthorpe.33:28
Mark Duffy sends in a cross, Michael Turner makes a clearance.31:37
Andrew Surman provided the assist for the goal.31:37 Goal scored
Goal! - Simon Lappin - Norwich 1 - 0 Scunthorpe Simon Lappin finds the back of the net with a goal from outside the area to the top right corner of the goal. Norwich 1-0 Scunthorpe.30:23
Wesley Hoolahan takes a short corner. Wesley Hoolahan delivers the ball, Mike Grella manages to make a clearance.28:55
Centre by Jimmy Ryan.26:20
The ball is crossed by Christian Ribeiro, Michael Turner manages to make a clearance.25:25
Steve Morison is flagged offside by the assistant referee. Sam Slocombe restarts play with the free kick.19:45
The official flags Andy Barcham offside. Free kick taken by Ryan Bennett.18:48
Steve Morison is caught offside. Sam Slocombe restarts play with the free kick.18:07
A cross is delivered by Marc Tierney, clearance made by Tom Newey. Andrew Surman takes the inswinging corner, Sam Slocombe makes a save.15:13
Mike Grella is caught offside. Indirect free kick taken by David Fox.13:55
George Francomb challenges Mike Grella unfairly and gives away a free kick. Jimmy Ryan takes the free kick.13:03
The ball is delivered by George Francomb, Chris Martin produces a overhead kick right-footed shot from deep inside the penalty box which goes wide of the left-hand upright.12:06
Chris Martin sends in a cross, clearance by David Mirfin. Marc Tierney sends in a cross, clearance by Niall Canavan.8:40
Josh Walker challenges Simon Lappin unfairly and gives away a free kick. Free kick taken by David Fox.7:07
David Fox takes the inswinging corner, clearance made by Sam Slocombe.3:21
Wesley Hoolahan takes a shot. Clearance by Christian Ribeiro. Inswinging corner taken right-footed by David Fox from the right by-line, Josh Walker makes a clearance.3:02
Foul by Mark Duffy on Marc Tierney, free kick awarded. Marc Tierney takes the free kick.2:15
Andy Barcham takes a shot. Save made by Declan Rudd.1:22
Marc Tierney sends in a cross.0:00
The ref blows the whistle to begin the match.
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