Paul Sturrock's side, knocked out of the FA Cup by Premiership Charlton last week, got back on track in the league as goals from Chris Brunt and skipper Graham Coughlan boosted their survival hopes.
Leicester, fresh from their impressive Cup victory over Tottenham, made the best of starts by snatching a seventh minute lead.
From a Gareth Williams corner Nils-Eric Johansson's header was half-cleared, but teenager Richard Stearman produced an acrobatic overhead-kick to crash the ball past Nicky Weaver from six yards.
Four minutes later Wednesday almost found the equaliser when Brunt's shot was blocked and Coughlan tried to force the ball in, but keeper Robert Douglas managed to block it on the line.
The hosts only had to wait until the 31st minute to pull level, thanks to a spectacular effort from Brunt, who slammed in a shot from 25 yards after neat link-up play with Glenn Whelan.
Brunt, in sparkling form, nearly snapped up the lead when he turned under pressure from three players and fired a difficult angled shot narrowly wide.
Wednesday continued to put pressure on the visitors and five minutes before half-time Sturrock's men moved ahead, when skipper Coughlan looped a textbook header over the keeper after a free-kick swung in by John Hills.
After a gripping first half the second period was a grim, scrappy stalemate as Leicester tried to find a way back but were held out by a stubborn Wednesday.
Williams hit an early shot well wide as Leicester signalled their intentions and another hopeful effort was off the mark from Joe Hammill. Another chance for substitute Iain Hume failed to trouble Weaver.
But Weaver needed to make a fantastic last-minute save to preserve the points when he dropped and held onto a stinging low shot from Mark De Vries.