The Owls played out a pulsating 3-3 draw with Derby County, who stayed in the division thanks to Martyn Waghorn's 78th-minute penalty.
Seconds before it was awarded, news filtered through that Cardiff City had equalised at home to Rotherham, meaning that the Owls' 3-2 lead was enough to keep them up.
But not for the first time, the visitors were sliced open, Colin Kazim-Richards picking out Martyn Waghorn on the left and when he played the ball across, the fit-again Chey Dunkley brought substitute Kamil Jozwiak down. Waghorn smashed the penalty home.
For all their desperation, Wednesday were unable to score a fourth. Teams are not relegated on a half of football but their poor defending had come back to bite them in the final 45 minutes.
They finished bottom of the table, relegated by three points at the end of a season which saw them deducted six for financial fair play breaches.
The first half was of low quality but at least much higher intensity than Wednesday's game against Nottingham Forest seven days earlier.
With heavy rain at the start of the game, conditions were better for slide tackling than mastery of the ball and it was reflected in the opening period. The second half was just too frantic to play any football.
Derby had the best chance of the opening half, but missed it, allowing the Owls to take the lead seconds before the interval.
Barry Bannan flashed an eighth-minute volley wide but it was the Rams who ought to have gone in front.
Callum Paterson, selected at centre-froward failed to deal with George Edmundson's long throw, and when Waghorn arrived at the far post from the corner he looked certain to score but hit the woodwork - literally - whilst the ball went wide.
He was able to play on after lengthy treatment. With Paterson and Jason Knight having also been down for a long time, a half that started later than Rotherham's had a decisive eight minutes added to it.
With the Owls so late out for the second half that the linesman was sent to fetch them, they were well ahead of the game at Cardiff City.
Adam Reach shot over when Edmundson cleared a corner to him, Kazi-Richards was flagged offside when he put the rebound from Keiren Westwood's save from Patrick Roberts into the net but goalmouth action was scarce until stoppage time when Kelle Roos saved Jordan Rhodes's header from a Paterson long thrown but Sam Hutchinson, marginally onside, put the ball in.
Wednesday's mental fragility saw them concede two poor goals in a matter of minutes shortly after they belatedly emerged for the second half.
Waghorn headed down a cross from the left in the 49th minute before Roberts curled another fur minutes later.
When Reach played a ball up from near the halfway line after 63 minutes Rhodes made a nuisance of himself and Paterson cooly drilled the loose ball in for an equaliser.
Soon they were in front, Dunkley - on his first appearance after an injury in February - headed a corner across goal and Julian Borner bundled it in.
It gave Wednesday the lead but with Rotherham ahead too, it was not going to be enough.
Soon, though, everything was turned on its head.
Wednesday threw everything at scoring a fourth after Waghorn's penalty, but they looked more likely to be caught out on the breakaway in their desperation.
It was asking too much to rescue a season - year, in fact - of mistakes in a manic final quarter of an hour.
Derby County: Roos; Byrne, Edmundson, Clarke, Forsyth (Buchanan 72); Knight (Bird 61), Shinnie (Jozwiak 72); Waghorn (Davies 82), Roberts, Lawrence; Kazim-Richards.
Unused substitutes: Marshall, Sibley, Cashin, Ebosele, Watson.
Sheffield Wednesday: Westwood; Hutchinson, Dunkley (Harris 87), Borner; Palmer, Pelupessy (Green 90), Bannan, Reach; Windass, Rhodes (Kachunga 79), Paterson.
Unused substitutes: Dele-Bashiru, Urhoghide, Shaw, Wildsmith, Hunt, Brennan.
Referee: M Dean (Wirral).
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