There was an unhappy return for Albion old boy Zander Diamond with an early own goal and the rampant home team added further goals before the break through Phil Edwards and Lucas Akins.
The Brewers went in front in the fourth minute after punishing a blunder by Shwan Jalal.
The goalkeeper’s clearance was charged down by Stuart Beavon and before the Cobblers could recover, the striker’s low cross was turned into his own net by Diamond.
Beavon caused more problems for the visitors, forcing Jalal into a save at his near post and then glancing a header onto the roof of the net.
A rocky Cobblers defence was exposed again in the 31st minute as Edwards clipped a Nasser El Khayati corner in off a post.
And more misery was heaped on the visitors four minutes before the break when Akins scored from the penalty spot after being upended by Evan Horwood.
Lawson D’Ath reduced the deficit with a stunning 15-yard volley in the 54th minute.
Northampton went on to dominate the second period but Burton held on to their two-goal advantage.