Derby had plenty of possession, but Preston kept them at arm's length for much of the 90 minutes and the only glimmer of hope for the home side was a dubious late penalty, which was missed.
Grzegorz Rasiak, one of two surprise inclusions in the Derby line-up, struck the 82nd minute spot-kick against the right-hand post and the ball cannoned away to safety.
It had looked a harsh decision to give the penalty in the first place and Preston thought they had stronger claims for a spot-kick turned down at the end of the first half.
In the end, it did not matter because the visitors were too solid and too well organised for Derby to break down, even with Spanish midfielder Inigo Idiakez in the team.
Idiakez had been ruled out until next season with a groin injury, but he was passed fit to play but could make little impact on the visitors.
The first half, for all the noise of a 31,000 plus crowd lacked any real incidents as Preston soaked up everything Derby threw at them.
The only moment of danger for the visitors came in the 34th minute when a quickly taken free-kick almost put Paul Peschisolido in, but Carlo Nash beat him to the ball and cleared.
Just before the interval Eddie Lewis appeared to be pushed in the back by Mo Konjic, but the referee awarded a goal-kick and Preston were as well drilled in the second half as they were in the first.
They almost scored in the 62nd minute when Lee Camp had to save at the feet of Brian O'Neil and Claude Davis when a corner caused chaos in the Derby defence and David Nugent should have finished the tie nine minutes from the end.
A cross from Paul McKenna gave him a chance at the back post but the young striker sidefooted wide from eight yards out.
It threatened to be a costly miss because Derby went straight up the other end of the field and Rasiak went over on the dead-ball line.
The referee stunned Preston by pointing to the spot, but Rasiak failed to score from 12 yards and Derby's last hope slipped away.