Hugill’s strike means that the Blades are now winless in five games and have also lost four of those five matches.
Victory for Preston in the first Championship meeting between the sides since 2011 lifts Alex Neil’s side to within two points of the play-off places.
Preston goalkeeper Chris Maxwell almost gifted Sheffield United an opener in the first minute by passing straight to the Championship’s top scorer, Leon Clarke, but Ben Davies rescued his keeper with a superb last-ditch tackle.
A lovely team move after 18 minutes triggered by Ben Pearson’s strong midfield tackle created an opening for Callum Robinson who drove into the area and fired an effort from 15 yards which was well tipped over by Simon Moore.
But Sheffield United had the better of the first-half chances, in particular through Chris Basham.
His first effort was a tame shot after 19 minutes from the edge of the area that was easily held before he was denied by a fantastic goalmouth block by Tom Clarke from a corner four minutes later.
But Basham came even closer after 25 minutes as his right-wing cross almost caught out Maxwell and brushed the top of the net on its way over.
It was Preston, though, who came the closest to opening the scoring in the first half as Paul Gallagher’s 40th-minute free-kick beat Moore and clipped the top of the bar.
And Neil’s side started the second half in the ascendancy, threatening with a swift counter-attack on 53 minutes as Tom Barkhuizen slipped Robinson clean through but he dragged the shot wide of the far post from 12 yards.
But a minute later Preston’s second-half pressure paid dividends as Robinson whipped the ball in from the left edge of the area and found Hugill who cushioned a volley in from six yards for his seventh league goal of the season.
Robinson was proving the main threat to Chris Wilder’s side and he almost doubled Preston’s advantage after 63 minutes after cutting in from the left flank before curling an effort that was comfortably held by Moore.
Sheffield United pushed for that equaliser but it was Preston who came closest as Hugill’s drive from 20 yards was inches wide of the far post one minute from time.
Manager Chris Wilder said: “I don’t like the spike that’s appeared in the team over the last few weeks. I don’t enjoy it. I am one for a consistent approach and performances and we are not getting it.
“I think some of them may have taken their eye off the ball a little bit. If that’s the case they (had) better get ready for the consequences of taking their eye off the ball.
“There have been a lot of plaudits gone to the club and to the players and the staff so we have to find an answer. Whether that’s personnel or my attitude towards them, we have to find a way.
“We need to improve. When you look at Preston, they have 25 established Championship players, that’s what we are up against. And Preston aren’t a big hitter in the division.”