Emil Riis grabbed a late equaliser to give North End a point at Bramall Lane and make it five games unbeaten, after Sander Berge looked to have given the home side all three points.
The Danish striker fired home from close range on the end of a Jordan Storey cross to take a deserved point back across the Pennines.
Substitute Berge looked to have won it with six minutes left, as he fired under Daniel Iversen from eight yards out, after Morgan Gibbs-White and Daniel Johnson had scored in the opening 20 minutes, setting up a finale where both teams were looking for the win.
North End, in green and yellow, started brightly, with a great move inside the final third, with Johnson floating a ball across for Josh Earl at the back post, who drilled a cross-shot back across goal, but no one was able to get on the end of it.
But on seven minutes United went ahead. Gibbs-White fired home with the Blades' first attack, Luke Freeman delivering from the left and a flick on from Iliman Ndiaye finding the former Wolves man on the penalty spot, where he hit a half-volley into the top right corner.
However, PNE were level in stunning fashion before the 20-minute mark. A brilliant ball from Ryan Ledson picked out the run of skipper Johnson, whose first touch was perfect to take it past the on-rushing Sweden No.1 Robin Olsen, and then slide the ball into the empty net from the edge of the penalty area for his 50th goal for the Lilywhites.
Eight minutes before the interval, more good play from Ledson saw him drill a ball into the feet of Sean Maguire 25 yards out, who turned and fired low from the edge of the box towards the bottom left-hand corner, forcing Olsen to get down to grab the ball.
With three and a half minutes to go until half-time, United had a rare chance to go back in front, some slick passing from left to right, eventually worked back into the penalty area for former Brighton man Oliver Norwood, but he fired over the bar from 15 yards when unmarked.
Olsen almost was the cause of his own downfall just before the hour mark, Maguire closing down the Swede, making a poor kick to Riis, who found former Blade Ben Whiteman, who in turn got it back to Maguire, but his shot was squeezed past the post.
Moments later, on the break Maguire held the ball up to feed Riis down the right; he breezed past Jack Robinson into the area, before firing a shot past Olsen, but also past the left-hand upright by a matter of inches.
With 13 minutes to go, there was a massive moment as John Fleck burst right through the middle, running 40 yards into the box, going one-on-one with Daniel Iversen, but the big Dane spread himself to make an almighty save and deny the Scottish international.
Then it was the turn of Olsen to make a huge save at the other end, this time Johnson beautifully crafted a ball which cut the middle of the pitch open for Riis to run on to. He fired on target, but the goalkeeper got a vital leg to it to take the ball over the bar and onto the roof of the pitch.
But the home side took the lead with six minutes to go when Fleck fed the ball through the middle into Billy Sharp, United’s captain miss-hitting into the path of Berge, who fired through Iversen’s legs and into the middle of the goal.
But with 30 seconds left on the clock, Riis grabbed a deserved point with his sixth goal of the season, drilling home inside the six-yard box after Jordan Storey’s excellent cross from the right recycled the ball into the middle after a free-kick from the middle of the pitch, sending the North End fans into ecstasy.
Sheffield United line-up: Olsen, Baldock, Fleck, Sharp (c), Egan, Freeman (Berge, 61), Norwood (Hourihane, 77), Robinson, Gibbs-White, Ndiaye (Brewster, 71), Norrington-Davies. Subs not used: Foderingham, Basham, McBurnie, Bogle.
PNE line-up: Iversen, Storey, Bauer (Murphy, 88), Hughes, van den Berg, Ledson, Whiteman, Earl, Johnson (c) (McCann, 84), Riis, Maguire (Potts, 70). Subs not used: Rudd, Cunningham, Lindsay, Browne.
Attendance: 25,463 (571 PNE fans)
Referee: Mr G Eltringham