Norwich, who had picked up just one point from their last four games, escaped when a poor clearance fell straight to the lurking Matt Kilgallon, whose shot on the turn from 15 yards flew inches over the target.
Billy Sharp, who scored his first league goal of the season in the midweek win over Coventry, should have broken the deadlock after Rob Hulse picked out the £1.8million striker, but Sharp miskicked five yards from goal.
Hulse, back in the side for the injured James Beattie, was foiled as United turned the screw, his close-range header from David Cotterill's teasing cross saved at the foot of the post by David Marshall.
The Sheffield side, dominant in midfield, were caught on the break as Kieran Gibbs burst through, his stinging shot from 20 yards beat Paddy Kenny but flew inches wide.
Hulse almost found a way through in the 36th minute, turning quickly to drill in a spectacular strike from 25 yards which beat Marshall but cannoned off the far post.
Norwich's reply was immediate, evergreen Darren Huckerby, back after a three-match absence firing inches wide before Matt Pattison drilled the ball over the bar from the edge of the area.
Cotterill, proving a handful on the right flank, almost carved out the opener minutes before the break his deep cross finding the hardworking Hulse who had to stretch and headed over from six yards.
However, after the interval the Blades got the goals that their play had deserved before the interval.
Sharp broke the deadlock as he stabbed the ball home from 12 yards in the 52nd minute from Cotterill's cross and the Canaries were beaten from that moment on.
Kilgallon soon added the second, stretching to meet David Carney's corner to finish with a crisp header from six yards.
Norwich battled to find a way back into the game as the clock ticked away, but they failed to mount a fightback and are back in the relegation shake-up after a recent slump in results.