Cobblers produced their most accomplished pre-season performance to date when a first-half goal from Marc Richards was sufficient to overcome Championship side Derby County in Tuesday's friendly at Sixfields.
Richards' tap-in just short of the half-hour mark gave the Cobblers a deserved lead at the break following an impressive first-half showing, before the home side withstood heavy pressure in the second to preserve their advantage and earn victory.
There are still some areas that will need work and improvement before next week's opener at Shrewsbury but otherwise it was an evening that yielded more positives than negatives for manager Justin Edinburgh, who would have been encouraged by how well-organised and fluent his side performed, first-half in particular, in just their second outing playing three at the back.
They became more ragged and disorganised after the break as Derby applied sustained pressure but the visitors were restricted to very few clear sights of goal and Town held on.
The headline team news saw Aaron Pierre and Matt Crooks both start for the first time, while Leon Barnett, Ash Taylor, Billy Waters, Daniel Powell and Dean Bowditch all had their first taste of walking out as a home player at Sixfields.
With Brendan Moloney absent and Aaron Phillips only on the bench, Powell started at right wing-back in a 3-4-1-2 with Bowditch stationed behind a front two of Waters and Richards.
Derby named a strong side themselves with David Nugent and Curtis Davies among the starters, alongside former Town duo Alex Pearce and Ikechi Anya.
But the more assured start came from Northampton, who controlled the opening exchanges and went close to an early lead when goalkeeper Jonathan Mitchell beat away Bowditch's weak effort following a fluid move involving Crooks, Richards and Powell.
The game's first clear-cut opening went to Derby, however, as Mason Bennett exposed a gap on the left side of Town's defence to work space for the shot which was beat away by a sprawling David Cornell.
Bennett flashed a second shot narrowly wide moments later but, just as the visitors seemed to be wrestling the initiative, it was the Cobblers who struck first.
Richards applied the finishing touch but the goal was all made by some sterling work from Powell. The former MK Dons man anticipated quickly to win the ball back in midfield before driving forward and feeding Waters, who paused, got his head up and picked out a pinpoint cross to where Richards had the simplest of finishes.
That was by no means an unfair reflection on the home side who had impressed going forward in the opening half-hour, though it was at the other end where at times they looked susceptible and again Derby squandered an opening when in behind, this time Nugent the guilty party as he fired wide.
But otherwise Derby were frustrated by the well-drilled and hard-working hosts, who then came within a whisker of making it two at the break when Barnett's powerful header from Matty Taylor's corner flew the wrong side of the post.
Edinburgh introduced Loen Lobjoit, Yaser Kasim and Regan Poole at half-time, and after a good start to the half, his side would have been pegged back on 54 minutes but for alert keeping from Cornell as he raced off his line to block at the feet of Marcus Olsson.
Derby's quality was beginning to show and they gradually upped the pressure as the second period progressed with Northampton, who were dropping ever deeper, having to rely on some last-ditch defending to keep their lead intact.
The second-half was quickly turning into a thorough examination of Town's defensive capabilities but, despite Derby pressing hard for an equaliser, the hosts remained disciplined and stood firm.
Despite having things all their own way, County were only able to carve out half chances at best and they were mopped up by Town who did enough to see out a victory that will stand them in good stead for the season ahead.
Cobblers: Cornell, A Taylor, Pierre (Poole 45), Barnett, Powell, Crooks (Kasim 45), M Taylor, Buchanan, Bowditch (Lobjoit), Richards (c) (Phillips 81), Waters
Subs not used: Goff, Smith
Derby: Mitchell, Bryson, Davies, Anya (Weimann 78), Baird, Pearce, Olsson, Butterfield, Bennett (Huddlestone 61), Hanson (Russell 61), Nugent (Martin 78)
Subs not used: Carson, Forsyth, Keogh, Johnson
Referee: Andy Woolmer
Derby fans: 813