Stephen Bywater made two saves early on from a Ross Wallace cross and corner.
Neil Mellor had a right-wing cross which led to Wallace having a shot saved at the near post.
Andy Lonergan saved from Derby's best player Kris Commons from a cross and corner.
Wallace, Commons and Rob Hulse all had shots saved before Preston took the lead.
Lewin Nyatanga fouled Chris Sedgwick and the free-kick and assist by Ross Wallace was hit home from six yards out by Sean St Ledger low into the middle of the net.
St Ledger fouled Hulse and Commons hit a direct free-kick which was saved and his resulting corner was also saved.
Before half-time Paul Green, Commons and Miles Addison had efforts saved.
Lonergan made saves from Commons and Nathan Ellington, and then Wallace curled a free-kick against the woodwork.
Martin Albrechtsen passed to Hulse and he had a shot saved and then substitute Nacer Barazite had a shot saved from an Albrechtsen centre.
Preston made it 2-0 after 68 minutes when Wallace again assisted with the cross and Jon Parkin from 15 yards out scored into the bottom left-hand corner of the net.
Wallace had another effort saved when he had a left-foot, right-wing free-kick, and then Commons had a cross saved and then finally Preston substitute Stephen Elliott who had replaced Neil Mellor had a shot saved in the final minute.
Preston will go into their next match at Barnsley looking for three more points to edge them towards the points safety tally for the season.