Derby moved second in the Championship table as Rams boss Billy Davies masterminded a win over his old club thanks to a Steve Howard double.
Derby took the lead in the 48th minute as Howard tapped in after Morten Bisgaard's shot was parried.
And Howard made it 2-0 from the penalty spot three minutes later after Jonathan Stead was fouled in the box.
Preston pressed and they pulled a goal back when David Nugent toe-poked the ball home from 12 yards on 79 minutes.
606 DEBATE: Give your thoughts on the match
Preston manager Paul Simpson on the second Derby goal, a penalty:
"From what people are telling me it's a shocking decision by a referee who has been very very weak.
"I don't think he knew what he was doing. There were some really clever time wasting tactics used and you hope the ref is strong enough to notice it.
"But we are judged on the result and it's rubbish for us because of two moments of madness in the second half."
Derby County boss Billy Davies:
"We are ahead of schedule, that's for sure. Nobody had thought for one second that we would be where we are in such a short period of time.
"We plan for a long term strategy but it's remarkable what we have done.
"But it's only three points. It's an enormous three points, but it is only three points. Forget all the euphoria."
Preston: Nash, Alexander, St. Ledger, Chilvers, Hill, Sedgwick (Whaley 61), Miller (Lewis Neal 75), Davidson (McKenna 62), Pugh, Nugent, Ormerod.
Subs Not Used: Lonergan, Wilson.
Booked: Davidson, Ormerod.
Goals: Nugent 79.
Derby: Bywater, Edworthy, Leacock, Michael Johnson, Camara, Jones, Bisgaard (Lupoli 69), Barnes (Malcolm 84), Oakley, Howard, Stead (Moore 88).
Subs Not Used: Grant, Seth Johnson.
Booked: Howard, Leacock, Oakley, Stead, Jones.
Goals: Howard 48, 51 pen.
Att: 19,204
Ref: L Probert (Gloucestershire).