A goal-less first half of very few changes saw both teams struggling to find their form with Rotherham going the nearest to breaking the deadlock.
Rotherham did most of the attacking, Daniel Nardiello shot over the bar after just two minutes and then from Ben Pringle's pass Alex Revell shaved the upright with a 10th minute shot. Johnny Mullins' header was deflected for a corner after 19 minutes and Nardiello's header after 38 minutes was wide of the target.
At the other end a bad back pass after eight minutes almost let in Pope, but he was penalised for a foul on Rotherham goalkeeper Andy Warrington and then Warrington denied Pope again after 35 minutes saving his header with his legs.
But ten minutes after the break it was Vale who got the vital breakthrough. Following a throw on the right Ryan Burge picked out Louis Dodds on the edge of the Rotherham penalty area and he slotted the ball wide of Warrington and into the net.
And worse was to follow eight minutes later for Rotherham. Their offside appeals were waved away and Vale's leading marksman Pope cut in from the left drawing Warrington out of his goal before planting his shot into the corner of the net against his former club.
Substitute Kieran Agard gave Rotherham some hope turning in a cross from fellow substitute Courtney Cameron
with seven minutes to go, but Vale held out to spoil Rotherham's Christmas.