Problems are mounting for under-pressure Barnsley manager Paul Hart as Adam Proudlock killed off the Tykes in a scrappy South Yorkshire derby.
The former Wolves striker grabbed the winner in the 24th minute and Hart now faces another crucial local derby clash against Doncaster Rovers on Wednesday.
Barnsley almost broke the deadlock in the sixth minute. Tom Williams found space on the left flank before picking out Chris Shuker whose angled header was snuffed out by David Lucas.
Wednesday took the lead when a long ball upfield found Steve MacLean. He twisted quickly on the byline and crossed low for Proudlock who netted with a close-range header.
Barnsley went close to snatching an equaliser five minutes later. Michael Chopra's fierce 12-yard strike was deflected past the post and from Shuker's corner the loanee from Newcastle United fired inches wide.
Proudlock then squandered a simple chance for the Owls in the 31st minute when he darted unnoticed into the box before volleying high over the bar.
Stephen McPhail's blunder set up a half-chance for Lewis McMahon but his long-range strike was smothered by the diving Ross Turnbull.
MacLean set up an opportunity for veteran Owls midfielder Chris Marsden immediately after the restart but the former Southampton star dithered and his low strike was blocked.
Proudlock tried his luck with a long-range left-footed strike but it flew high over the bar before Chopra almost grabbed the equaliser when his angled drive was tipped over the bar in spectacular fashion by Lucas.
Patrick Collins headed wide after neat work by substitute Graeme Lee before Collins saved the Hillsborough side with a last-ditch tackle on Michael Boulding as the Barnsley substitute surged into the area.
Turnbull foiled Proudlock in the dying minutes when he bravely dived at the striker's feet before grabbing the ball at the second attempt as McMahon charged in. He then blocked John Paul McGovern's fierce drive as Wednesday ran out deserved winners.