In his first game of the season he scored one and helped set up the other, to send the relegated Premiership side crashing again.
The Blades have now taken just one point from five away games, while City, up from League One, are fourth in the table.
Apart from a dodgy spell early in the second half, the Robins were the better side, and when Michael McIndoe headed their second goal, with just under 20 minutes left, Noble, his work done, was taken off.
He had been brought into the side to replace Lee Trundle, a £1million summer signing from Swansea City, who was dropped after scoring just two goals in ten games.
Noble's lack of match sharpness showed up at times but he was perfectly placed to score his goal right on half-time, from a throughball by Lee Johnson. It took a deflection before Chris Morgan tried a back header, which fell short.
As defenders panicked, Noble was there with the final touch to steer the ball away from a desperate challenge.
The goal was deserved, for City were by far the more enterprising with Bradley Orr as a raiding right-back pushing ball after ball down the channels.
He almost got a goal too, when he went up for City's first corner in the 16th minute but his header was pushed on to the bar by United keeper Paddy Kenny.
The home goal had a rather similar escape in first-half stoppage time when Adriano Basso turned a drive from Alan Quinn against his right post.
Sheffield United had so nearly gone ahead in the first minute with a rebound off home skipper Louis Carey, but with Lee Hendrie picking up a knock which saw him miss the second half, the build-up for their attack was patchy and James Beattie had few chances to add to the eight goals he has scored since moving from Everton in the summer.
There was always too much tension inside United's game although they came close to pulling it together midway through the second half. A fierce shot from David Carney was turned away by Basso for a corner, which brought a sharp but unlucky header from Chris Lucketti.
But in the end the Blades deservedly lost as the pressure grows on beleaguered boss Robson.