In an electric opening 45 minutes, Town netted twice in quick succession to put themselves in a commanding position.
Tristain Abrahams grabbed his third goal for the club from the penalty spot before Jake Gray continued his scoring form with a fine finish on 24 minutes.
With two goals in as many games, the winger had a third ruled out as the half drew towards a close in an otherwise flawless half.
Not putting a foot wrong in the first-half, the visitors were punished early in the second when miscommunication ended with Omar Sowunmi heading into his own net.
A disastrous second half continued when Daniel Powell levelled the score before the hour-mark, combining with scores elsewhere to make retaking the lead pivotal if survival was to be carried over to the final fixture.
Alex Fisher and Bevis Mugabi both went close to sparking pandemonium amongst the travelling faithful but it wasn’t to be as relegation fears were realised.
Encouraged by Easter Monday’s performance in the 1-1 draw with Colchester, Neale Marmon was forced into making just one change to his starting eleven.
Ruled out for the remainder of the season with a hamstring injury, Rhys Browne was replaced at right-back by Matt Worthington in the only alteration.
Needing an attacking display on the road, four strikers were named on the bench including Ryan Seager who returned after a game’s absence with a knee injury.
Knowing defeat could cost their league status depending on results elsewhere Marmon’s side were quick to try and take the initiative.
With just two minutes on the clock, a swift counter ended with Tom James switching play to Monday’s scorer Gray, who almost made it two in as many games but for his strike to nestle in the side netting.
Almost caught out in the opening exchanges the Cobblers began to see more of the ball and created their first genuine chance just before the quarter-of-an-hour mark.
In a combination of two former Town players, Sam Hoskins headed back across goal for Andy Williams whose acrobatic effort had to be tipped around the post by an alert Nathan Baxter.
However, before the hosts could build up a head of steam the Glovers were awarded a glorious chance to take the lead when Sowunmi was hauled down in the box from a James long throw-in.
With 19 minutes on the clock, Abrahams took the responsibility from 12 yards and had ice in his veins to send David Cornell the wrong way and slide the ball into the bottom corner.
Having silenced the home crowd the green and whites set about creating elation in the away end for a second time just six minutes later.
Superb hold-up play from Courtney Duffus resulted in a neat reverse pass that spotted the run of Gray, who showed supreme confidence to the lift the ball over an onrushing Cornell from close range.
In dreamland, Northampton almost brought Town back down to earth when Williams forced Baxter into another save on 30 minutes but Marmon’s side were soon back on the offensive.
Robbing the Cobblers of possession on the halfway line, Sessi D’Almeida threaded the ball through for Gray who wasted no time in firing into the back of the net but for the linesman’s flag to rule out the effort for offside.
Almost unplayable and not to be deterred, Gray had his sights on goal again just before the break when the ball sat up invitingly on the edge of the box but for his rasping volley to fly inches wide, as the Glovers settled for a comfortable lead at the halfway stage.
Rarely tested by Keith Curle’s side in the first-half the Glovers provided them a cheap lifeline just four minutes after the restart.
Williams’ cross from the left should’ve been dealt with, but instead was diverted into the back of his own net by Sowunmi to throw the game wide open.
Giving the hosts hope and sensing nervousness amongst Town’s ranks, Yeovil’s lead was wiped out on 56 minutes.
Joe Powell’s through ball was perfectly into the path of his namesake who made no mistake picking out the bottom corner to plunge the green and whites back into the relegation zone.
With the pendulum of momentum now in favour of the Northamptonshire outfit, the opportunities to take the lead fell to the side in claret.
Hoskins volleyed into the arms of Baxter, Williams fired into the side netting and Joe Powell drove just wide as the pressure mounted.
With scores elsewhere conspiring against the green and whites they had to go for broke in search of a third as Francois Zoko, Yoann Arquin and Fisher entered the fray.
With caution thrown to the wind and numbers thrown forward, the Glovers had two late chances to salvage a result.
James’ wide free-kick to the back post looked destined for the back of the net when it landed on the head of Sowunmi, but only directing his head back across goal Fisher wasn’t able to apply the finishing touch.
Entrenched in the Northampton half Arquin had his 25-yard volley somehow parried away by Cornell but it wasn’t to be, as the fight to beat the drop came to an end on the road.
Northampton Town: Cornell; Goode, Pierre, Turnbull; Hoskins, Foley, Bowditch (Bridge 72′), Cox (McWilliams 61′); J. Powell; D. Powell, Williams.
Bookings: McWilliams 75′, Foley 90′
Subs not used: Coddington, Buchanan, Elsnik, O’Toole, Morias.
Yeovil Town: Baxter; Worthington, Sowunmi, Mugabi, James; Gray (Fisher 84′), Pattison, D’Almeida, Abrahams (Zoko 70′); Duffus (Arquin 75′), Dobre.
Subs not used: Nelson, Ojo, Rogers, Seager.