Irvine, 51, was surprisingly sacked by Preston in December, despite an impressive two-year tenure in which he saved the Lancashire outfit from relegation before guiding them into the Championship play-offs last season.
The Owls quickly snapped up Irvine to lead their battle against the drop, and his players illustrated their stomach for the fight with a stirring second-half comeback on Tuesday night.
Neil Mellor fired Preston ahead in the 29th minute and when influential midfielder Paul Coutts added a second eight minutes after the restart, it looked all over for Irvine.
Yet the former Everton assistant boss has fashioned a side with guts. They hit back with a speculative effort from distance by Tommy Miller in the 53rd minute and Marcus Tudgay's superb finish drew the Owls level four minutes later.
Irvine lost winger Jermaine Johnson to injury after just nine minutes, replacing him with Tom Soares, but the visitors should have soon led when Luke Varney headed Eddie Nolan's cross straight at goalkeeper Andy Lonergan.
Moments later, Preston winger Ross Wallace found Matt James and the on-loan Manchester United midfielder drove a 25-yard shot narrowly over the crossbar.
Tudgay saw a close-range strike saved by Lonergan in the 24th minute before Preston established control through Mellor's clinical opener.
Coutts' delightful pass dissected the Wednesday defence and allowed Billy Jones to strike at goal.
Jones' low shot was blocked by Wednesday skipper Darren Purse but Mellor tucked away the rebound with a low right-foot shot.
Ten minutes before the break, Mellor almost doubled Preston's advantage with a powerful run forward and left-foot drive which Lee Grant tipped over the bar.
The onus was on Wednesday to find a response after the break but Preston struck again in the 53rd minute when Coutts engineered space inside Wednesday's 18-yard box and squeezed a low right-foot shot past Grant from an acute angle.
The goal seemed to jolt Wednesday into life and four minutes later they were off the mark when Lonergan inexplicably allowed Miller's 30-yard piledriver to slip into the net.
The Owls continued to pour forward and were rewarded on the hour when Tudgay took advantage of another defensive slip in the home ranks and clipped a delightful finish over the advancing Lonergan and into the net.
Wednesday, roared on by a sizeable contingent of travelling fans, looked the more likely victors as the game wore on. Lonergan produced fine saves to deny substitute Leon Clarke twice in quick succession in the closing stages as Irvine was forced to settle for a point.