Cobblers produced their best performance of the season by a country mile to earn unquestionably their most impressive three points as they stunned promotion-chasing Bradford City with a fully-deserved, if somewhat tense, 2-1 victory at Valley Parade on Saturday.
For so long Town fans have been waiting for their team to fulfil their potential and put in a display like this one as they controlled the first-half and early parts of the second to go into a 2-0 lead before defending with heart and nous to come away with a valuable victory, their second in succession.
The Cobblers not only held their own first-half, they were the better side for long spells and had done enough to warrant a lead at half-time, given to them by John-Joe O'Toole's towering header.
Chris Long then added a second goal on the hour-mark but Bradford did not give up lightly and a late goal got nerves jangling among the away fans, however the full-time whistle confirmed victory and a worthy one at that.
Town remain in the relegation zone but this result might be the one that finally kick-starts their season and gives them the confidence to pull clear of the bottom four.
Two debutants featured in the Cobblers team as Jimmy Floyd Hasselbaink's most recent recruits Richard O'Donnell and Jordan Turnbull lined up in goal and at left-back respectively, meaning David Buchanan dropped to the bench for the second time in three games and Ash Taylor captained the side.
The Cobblers made more than just a steady opening to the game, even having the better of the early exchanges and it was skipper Taylor who almost rewarded that strong start when side-footing Matt Grimes' corner just over the crossbar.
Grimes' delivery from set-pieces would create headaches for Bradford all half while Alex Gilliead caused one or two problems for the visiting defence but chances were at a premium for most of a first-half that struggled to spark into life.
That all changed in the moments leading up to half-time, however, when goalmouth action came at both ends.
The City fans, who were far from pleased with their side's efforts and made that displeasure known, were up and celebrating when defender Matthew Kilgallon diverted into the net after O'Donnell spilled Paul Taylor's fizzing free-kick, but the offside flag had been raised long before.
Back up the other end, Lukas Raeder also made his first save of the game when getting down quickly to keep out Sam Hoskins' low stinger, and then it was O'Donnell's turn to again be called into action as he produced a flying save to tip Romain Vincelot's volley over the crossbar.
All of a sudden, as half-time approached, the game had come to life and there was still time left to the breakthrough to come prior to the break.
Bradford's marking had been questionable throughout the opening 45 minutes and they were finally made to pay by their visitors as O'Toole was left all alone to head in Grimes' corner.
Town had gone into this game as firm underdogs but few of those in attendance at Valley Parade could begrudge them the lead at the break, certainly judging by the boos from some home fans.
Inevitably, the second period began with Bradford on the attack and having an awful lot more possession than they did in the first, however O'Donnell's goal remained relatively untroubled.
Not only that, the Cobblers were still carrying a threat in the final third and that was exemplified when they stunned their hosts with a second goal just after the hour mark.
O'Toole was again involved, this time getting in-between the Bradford defence to slip in Long who took a touch to get the ball out of his feet and then wrong-foot Rader to put Town into a shock 2-0 lead.
The Bantams, now desperate for a way back into the game, applied further pressure but only really managed half chances from the edge of the box until the 73rd minute when Taylor stood firm to block Knight-Percival's close-range shot.
Bradford's pressure built and built and in the final six minutes they miraculously failed to pull a goal back with the mother of all goalmouth scrambles.
Three or four times they looked destined to score but O'Donnell pulled off a couple of superb reaction saves before Regan Poole got back to hook off the line.
In the next attack, Dominic Poleon bore down on the Town goal but could only crash the ball off the crossbar and the visitors weathered that period of relentless pressure.until stoppage-time.
Five minutes were added and it was enough time for City to crank up the tension as Paul Taylor's quickly-taken free-kick caught O'Donnell out at his near post and halved the deficit.
Bradford piled forward thereafter but Northampton, who had defended with such courage throughout, clung on for a victory could prove invaluable in the context of the season.
Bradford: Raeder, Hanson (Guy 66), Knight-Percival, Kilgallon, Robinson, Gilliead, Vincelot (c), Dieng, Law, Taylor, McCartan (Poleon 72)
Subs not used: Sattelmaier, Pybus, Reeves, Devine, Gibson
Cobblers: O'Donnell, Facey, Poole, Taylor (c), Turnbull, Crooks, Grimes, O'Toole (Pereira 88), Foley, Hoskins (Powell 76), Long (Revell 86)
Subs not used: Cornell, Moloney, Buchanan, McWilliams
Referee: Craig Hicks
Cobblers fans: 393