Irish winger Keith Treacy was North End's saviour with a last gasp strike to claim all three points for the Lilywhites.
Treacy capped a man of the match performance to grab his second goal in the space of a week, the winner in a five goal thriller, in the last seconds of injury time.
The goal sparked scenes of wild celebration around Deepdale after what was yet another rollercoaster afternoon of football for Darren Ferguson's team - thankfully this one a happy ending.
"We were playing for our careers," Treacy said after the game.
"Nobody wants to go down to League One and thankfully we have all but secured our place in this division and that's nice. It was a bit up and down but we are delighted to get the win in the end, especially the way we did."
North End looked comfortable after taking a first half lead through a Jon Parkin effort in the 28th minute, but they looked to have thrown it all away when a second-half Gary Thompson brace put Scunthorpe in the driving seat. But Billy Jones grabbed an equaliser four minutes before the end before Treacy's heroics saved the day.
Treacy said: "We were on a high when we got the first goal and then obviously they went ahead and it was a bit of a downer and the crowd were starting to get a bit annoyed and I think we started feeling really tired and your head starts to take over and telling you are losing but we managed to get a couple of goals and get ahead and that's us safe now so we can take the shackles off and start to play with a bit of freedom now.
"I just want to keep playing, keep fit over the summer and then concentrate on next season. We don't want to be down this end of the table this time next year and I am sure we won't with the Gaffer behind us."
The Irish midfielder said his strike was up there with his best but then admitted that it wasn't hard bearing in mind he had only scored three goals in his professional career.
"I cut inside and I only had one thing in my head and I thought I might as well try and bend it in, thankfully for me it has gone past the goalkeeper and in.
"It's up there with my best, but I've only scored three goals in fifty odd appearances, it's not great hopefully I can score a couple more."
