Crystal Palace revived their play-off hopes but added to Preston's relegation worries thanks to Clinton Morrison.
Palace dominated the first half but Ben Watson hit his shot wide while Morrison and Paul Ifill had efforts saved.
Preston tried to push for a winner after the break but Chris Sedgwick's 20-yard effort was tipped over the bar while Lewis Neal's shot was blocked.
It was Palace who broke the stalemate when Morrison received a Victor Moses pass and headed in from six yards out.
Preston boss Alan Irvine:
"It was a poor performance. Palace deserved to win. I don't think we looked threatening enough.
"We looked a bit more threatening in the second half. We got a bit more momentum, then conceded an unnecessary corner from which they scored the goal.
"We didn't pass the ball well enough, didn't receive the ball enough."
Crystal Palace boss Neil Warnock:
"We were really resolute. In fairness to Preston, I think the Stoke game took a lot out of their sails.
"Because of the movement of the front three and the midfield, we got a lot of the ball. We played it very well, long and short and were quite professional.
"It's probably one of the best team performances of the season. Everyone was very good in their own right."
Preston: Lonergan, Jones, Mawene, Chilvers, Hill, Sedgwick (Ormerod 82), McKenna, Carter, Whaley (Lewis Neal 46), Brown, Hawley (Mellor 46).
Subs Not Used: Chris Neal, St. Ledger.
Booked: Jones, Carter, Hill.
Crystal Palace: Speroni, Butterfield, Hudson, Lawrence, Hills, Ifill (Freedman 61), Watson, Fletcher, Derry, Morrison, Moses (Robinson 87).
Subs Not Used: Fonte, Hughes, Scannell.
Booked: Moses, Ifill, Watson.
Goals: Morrison 76.
Ref: Michael Jones (Cheshire).