The Hillsborough side have been transformed since the sacking of Paul Sturrock, and were chasing their fifth successive home victory with new manager Brian Laws in the Wednesday hot-seat.
Wednesday, playing with all the confidence missing in their poor start to the season, caught out the Cardiff back four in the opening minutes, Deon Burton nipping in to fire a right-foot drive inches over the target from just inside the area.
They were handed an even better opportunity after midfielder Wayne Andrews, signed on loan from Coventry in place of the suspended Wade Small, was chopped down on the edge of the box, Kenny Lunt firing the free-kick through a gap in the wall but straight into the arms of Neil Alexander.
Cardiff, whose lead at the top has been chipped away after two defeats in their last three games, caught out Wednesday on the break. Paul Parry's looping cross from the right was flicked on by Michael Chopra to the waiting Riccardo Scimeca who ballooned his 15-yard volley high over the top of the bar.
Playmaker Stephen McPhail pulled a couple of free-kicks inches over the Wednesday woodwork before centre-back Madjid Bougherra caught Cardiff flat-footed as he broke quickly from defence.
The big defender sprinted half the length of the pitch before picking out Andrews on the right flank but, with time to spare, the former Crystal Palace winger squandered the opportunity drilling in a low shot from the edge of the area that was scooped up by Neil Alexander at the near post.
The Cardiff keeper foiled Andrews minutes later after he evaded a lunging tackle from Sheffield United full-back Alan Wright, starting a one-month loan spell with Cardiff.
Andrews quickly got down to smother the ball before Bougherra almost broke the deadlock heading a Lunt free-kick over the bar from eight yards under pressure from Alexander.
The Sheffield side should have snatched the lead in the 54th minute after a darting run by Frank Simek down the right wing. The little full-back cut inside to pump a low centre across the face of the goal with Marcus Tudgay, substitute Steve MacLean and Yoann Folly all failing to connect.
A rare mistake by Bougherra let in Michael Chopra minutes later when he slipped as he tried to clear eight yards from goal. The former Newcastle striker pounced quickly but was foiled by Lee Bullen, the 35-year-old defender sticking out a foot to block his shot with keeper Mark Crossley helpless.
Andrews pulled a right-foot strike inches over the target before Alexander saved the Welsh side again. MacLean robbed Parry on the left and darted towards the area, the ball was pulled across to the little winger who finished with a stinging shot, pushed round the post by the Cardiff keeper.
Wednesday escaped 14 minutes from time, Chopra picking out Parry whose low drive from 16 yards beat the diving Crossley as Lunt hooked the ball off the line.
Minutes later the Wednesday keeper pulled off a stunning reflex save to keep out Joe Ledley's close-range header as the match ended goalless.