Richard Chaplow's 77th-minute equaliser ensured Preston's unbeaten start to the season continues.
The hosts took a deserved lead after 20 minutes when Sean McAllister timed his run to perfection to smash home from a long throw-in.
Wednesday could have stretched their lead but Jermaine Johnson shot wide from six yards and Deon Burton had a header blocked on the line.
And Chaplow made the Owls pay by rifling home Chris Sedgwick's cross.
Sheffield Wednesday boss Brian Laws:
"There is a tinge of disappointment because the first-half performance was unbelievable.
"It was fantastic to watch, both wingers were on form and how we came in only 1-0 up amazed me.
"That's football though. You have to take your chances when they come and I did say at half-time that Preston would have a spell themselves."
Preston manager Alan Irvine:
"We didn't work well enough in the first half and Wednesday deserved their lead.
"But after the break we were a lot better. We definitely finished the game stronger and could have won it.
"Everyone would probably like to think I went in at half-time and went ballistic but I didn't. I kept a calm head."
Sheff Wed: Grant, Spurr, McMahon, Beevers, Wood, McAllister, Esajas, O'Connor, Johnson (Smith 71), Tudgay, Burton (Clarke 87).
Subs Not Used: O'Donnell, Gilbert, Watson.
Booked: Burton, Esajas.
Goals: McAllister 20.
Preston: Lonergan, Mawene, St. Ledger, Hill, Jones, Chaplow, Sedgwick, Nicholson (Wallace 55), McKenna, Whaley (Hawley 60), Mellor.
Subs Not Used: Chris Neal, Carter, Hart.
Booked: Hill.
Goals: Chaplow 77.
Att: 17,963
Ref: Mike Russell (Hertfordshire).
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