Matt Ingram's own goal on 12 minutes handed Northampton the lead but just six minutes later Pierre, on loan from Brentford, struck to keep Wanderers out of the drop zone on goal difference.
Northampton, who have been in the bottom two since September, temporarily edged out when Ricky Ravenhill's speculative effort from distance, combined with an error by home goalkeeper Ingram, saw the Cobblers take the lead.
But on 18 minutes Wycombe were level. Pierre headed across goal into the corner of the net from Matt Bloomfield's free-kick after a foul by John Marquis.
The Chairboys had the better of the second half chances, hitting the bar through Dean Morgan's header from a Sam Wood cross while Matt McClure headed narrowly over the frame of the goal from a corner.
Both sides are left locked together with Bristol Rovers on 47 points at the wrong end of the table with just three games remaining.