Former Barnsley striker Sam Winnall was minutes away from posting a triumphant return to his old stamping ground only to see Angus McDonald hit an injury time equaliser.
Winnall struck first just after half time in a game that could have gone either way before McDonald earned a point right at the last.
A draw was probably the right result overall as the Tykes and the Owls battled for the bragging rights that were ultimately shared.
A cagey derby opening saw the lion’s share of possession in midfield as both sides jostled for the advantage.
And a full 15 minutes passed before the first sight of goal when Tom Bradshaw dragged a snapshot wide for the hosts.
The stalemate continued as only scraps were served in the final thirds at each end of the field – Adam Hammill glanced a low header straight at Keiren Westwood midway through a tight first half.
Wednesday suffered a blow when Sam Hutchinson was forced off ten minutes before the break before the Owls fashioned their first real opportunity.
Barry Bannan swung a deep cross to the far post and the clearance fell to Callum McManaman but the winger’s shot flew just over the bar.
The loanee winger then drilled a long ranger that narrowly missed the target as the Owls ended the half on the back of their best spell so far.
And that upturn was extended five minutes into the second half as Wednesday took the lead.
Adam Reach refused to give up on a hopeful punt down the right flank, forcing goalkeeper Adam Davies into an error.
Trying to shepherd the ball out of play, Davies had his pocket picked by Reach and Winnall pounced to side-foot calmly into an unguarded net.
The contest opened up and Morgan Fox made a superb last-ditch challenge to deny Alex Mowatt and Barry Bannan hit a fierce drive from distance over.
Reds substitute Adam Armstrong almost had an immediate impact but was thwarted by the out-rushing Westwood as the Tykes sought to restore parity.
Play was soon back in the Barnsley box, though, and McManaman stabbed goalwards but straight into the grateful arms of Davies.
The energetic Reach curled just wide with the clock ticking down and just as the Owls were heading for victory, Barnsley struck at the last.
Hammill’s set piece was hit into the heart of the danger zone and McDonald headed home.
Still there was time for more drama as Westwood saved from Armstrong and then Fox cleared a Hammill hit off the line right beneath the bar.
Wednesday: Westwood, Hunt, Loovens, Lees, Fox, McManaman (Matias 73), Bannan, Hutchinson (Jones 35), Reach, Rhodes (Fletcher 64), Winnall