The Blades went behind inside ten minutes due to slack defending which allowed Ched Evans to squeeze past his markers to splash home past a bewilder Paddy Kenny.
From then on, United barely controlled the first half with neither side looking to rumble the net, but in the second half things were different, after bringing on Billy Sharp who gave an inspiring performance which alone gave him Man of the Match status. The Blade hustled and bustled to no prevail until the final minute when Kilgallon headed home only to see a offside flag waved against him.
Sheffield United had gone five games unbeaten away from home prior to their game at City which was ended by a Canaries team rejuvenated by new manager Glenn Roader who now move out of the bottom three of the Championship.
The home side kicked off attacking the Barclay End and could have earned their lead earlier on if Paddy Kenny hadn't kept out Darren Huckerby's effort with his legs.
The former Newcastle United and Coventry City striker then slashed in some important crosses which evaded everyone, but in 10th minute his left wing cross was headed skywards by defender Gary Cahill before Jimmy Smith headed to Ched Evans who looped the ball home from six yards.
Defender Martin Taylor then found Jamie Cureton through on goal but his attempted lob over Kenny flew over the crossbar. However he came close later on when he headed straight at the keeper following Mo Camara's cross.
At the start of the second half Keith Gillespie fired wide of the mark and ten minutes in David Marshall kept out David Carney's shot before Kenny did the same at the other end with Huckerby on fire.
Blades boss Bryan Robson made wholesale changes; brining on Billy Sharp in place of Chris Armstrong to revert to a much needed 4-4-2 formation and made an immediate impact; firing wide at the angle on the half-volley.
Michael Tonge then pulled out a save from Marshall and to add pressure to the United defence Dion Dublin replaced Evans for City
Acting as his usual Defender/Striker role the veteran was plunged more in his own penalty area and the Blades finally broke the deadlock in the last minute of the game.
With the Canaries under the cost Keith Gillespie produced a killer cross from the right hand side which with three players attacking found defender Matthew Kilgallon who headed home from close range.
The away fans went crazy as the ball bundled over the line but a late offside flag denied the Blades from taking a point.