Adam Reach scored in the final moments at Deepdale
Adam Reach's injury-time equaliser - his first goal for Sheffield Wednesday - rescued a point for them at Deepdale.
Preston went ahead when Sam Hutchinson turned Callum Robinson's cross into his own net with 13 minutes remaining, and Aiden McGeady almost doubled the lead when his 25-yard shot struck the post.
Reach, who spent last season on loan at Preston, then fired into the top corner from inside the penalty area.
Earlier, Simon Makienok headed wide from Robinson's first-half cross.
Promotion-chasing Wednesday had won their previous three matches without conceding a goal.
However, without injured striker Fernando Forestieri, they struggled to create openings and were on the back foot for much of the game.
When the visitors eventually threatened, Paul Huntington's last-ditch challenge prevented Steven Fletcher scoring from Barry Bannan's cross.
Fletcher then headed wide, again after being found by Bannan, before Reach hauled the Owls level.
Wednesday remain sixth in the Championship table and Preston are 13th.
Wednesday hit back after Sam Huthinson's own goal
Sheffield Wednesday manager Carlos Carvalhal told BBC Radio Sheffield: "Adam Reach didn't perform so well but he is a player that will fight a lot and run a lot.
"We tried to keep the ball and expected to play more in the offensive half and get more crosses in.
"But Preston gave us problems, so we tried to do different things and tried to do things with pace.
"The one player we have with pace is Reach, so we put him in a more attacking position."
Preston manager Simon Grayson: "When the opposition score so late in the game it's hard to take.
"But when you look at how well we played and how much we dominated, we can be very proud of our performance.
"The players played very well and made a very good team look very average. Sheffield shouldn't have got anything out of the game.
"We just couldn't get the ball cleared at the end. We needed one really good clearance. If we had done it would have been game over."
