Hereford recovered from conceding a goal inside the opening 30 seconds to record their first away win of the season at Sixfields.
Goals by Darren Jones, Mathieu Manset and substitute Craig King turned around the early lead given to the Cobblers by Ryan Gilligan's seventh of the season and secured a 3-1 triumph for the Bulls.
The early drama saw Adebayo Akinfenwa slip past Ryan Green and deliver a low cross which Gilligan tucked home at the back post.
The Bulls were level in the 15th minute when the home side failed to deal with a Jordon Mutch corner and centre-back Jones drilled home from close range.
Both sides had chances before the break, with an Andy Holt volley being parried away by Adam Bartlett while Jonny Godsmark made a glaring miss, firing over a Marc Pugh cross from three yards.
Hereford went in front in the 57th minute when a Mutch blockbuster was pushed skyward by Chris Dunn and Manset reacted quickest to head home.
Holt saw a near-post effort deflected onto the roof of the net but the Bulls wrapped up the points 14 minutes from time when King kept his cool to control and convert a byline cross from Pugh.
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