Paul McVeigh broke the deadlock with a 69th minute goal to end Norwich's run of just one win from nine games to leave Blades boss Neil Warnock with problems as he tries to lift his side.
Ndlovu almost broke the deadlock in the sixth minute as he ran from midfield with Craig Fleming and Adam Drury in hot pursuit.
Ndlovu lashed in a fierce left-foot shot, the ball cannoning of Robert Green's chest as he charged off his line and centre back Fleming hooked the loose ball clear.
United carved out another opening but squandered the opportunity with Ndlovu again involved. Michael Brown spotted Ndlovu in space on the right and the United midfielder picked out Tommy Mooney who powered his header high over the target from close range.
Norwich, pegged back by the Sheffield side, were handed a chance after a rare mistake by Stuart McCall. His poor clearance found David Healy who finished with a low shot that was pushed round the post by Paddy Kenny.
The former Bury keeper produced an even better stop minutes later tipping Paul McVeigh's long-range strike over the top with big Iwan Roberts heading a Clint Easton corner over the United bar.
Fleming linked neatly with Healy before lashing the ball across the face of the United goal with Roberts inches away from adding the finishing touch. The Norwich skipper produced a stunning volley seconds later as he connected with a Healy cross and Kenny, guarding his post, snuffed out the danger.
The United keeper foiled Steen Nedergaard spectacularly palming his 25-yard shot over the bar before the Sheffield side were reduced to ten men in the 61st minute when full back Quinn was sent off for a foul on Healy after picking up a yellow card in the first half.
McVeigh hit the winner in the 69th minute, Gary Holt feeding the little striker who cut inside substitute Nick Montgomery and beating Kenny with a right foot strike from 15 yards. Ndlovu was ordered off a minute from time for his second bookable offence.