Skipper Lee Dickson scored his fifth try in four games as Saints secured a superb 20-15 win at Aviva Premiership table-toppers Saracens.
Jim Mallinder’s men put in a fine performance at Allianz Park, where they have won on three of their four league visits since the ground opened in January, 2013.
Saracens had gone 6-0 up through two Ben Spencer penalties, but Stephen Myler responded with a try and conversion.
In an ebb and flow game, Sarries retook the lead before the break, with Alex Goode landing a penalty while Spencer was in the sin bin.
But Saints had dominated possession for long periods during the first half, and they started superbly in the second, with Dickson darting over.
Sarries responded with another couple of penalties, but the assured boot of Myler ensured Saints would get over the line for a superb success.
The home side ended the game bemused as their fly-half, former Saint Nils Mordt, booted the ball out to ruin any chances of a late try that could have helped win the game.
Saints didn’t care as they enhanced their top-four hopes with a second successive win, following the victory over Worcester Warriors a week earlier.
Buoyed by that big Franklin’s Gardens success and the fact Saracens were missing so many England stars, Saints pushed on in the formative stages of the game at Allianz Park.
But the home side stood tall to the waves of attack, stopping their visitors from reaching the 22.
At the other end, the home side looked dangerous and after good work from England men Goode and Jamie George, they won a penalty.
Spencer kicked it to earn a 16th-minute lead for his side, but they were soon being forced to defend again, stopping two Saints forward surges and turning the ball over.
And it was Saracens who were the ones scoring the points as Mike Haywood was penalised in front of the posts, giving Spencer another easy three points.
But the scrum-half and goalkicker was soon heading to the sin bin as Saints, who had lost Courtney Lawes to injury moments earlier, turned the screw.
They eventually got some reward for a first half on the front foot as Jamie Gibson charged down a clearance and Tom Wood teed up Myler, who weaved his way through for a clever score.
The Saints fly-half added the extras to give his team a one-point lead, but they couldn’t hold onto it going into the break as Sarries won a penalty at the scrum and Goode kicked it.
Spencer returned a minute after the interval with his team 9-7 up, but, almost immediately, Dickson showed superb awareness to stretch out a hand to score.
Myler converted superbly and Saints thought they’d scored again just after as Ben Foden dived over in the corner.
But referee Tom Foley went to the TMO and spotted that Foden had knocked on while being challenged by Michael Rhodes.
Saracens made the most of their reprieve by cutting the gap to two points at the other end, with Spencer landing a penalty.
But Myler replied after Saints won a penalty at the scrum and a big 15 minutes were in prospect with just five points separating the sides.
Goode reduced the arrears to two when Dickson was caught offside at a scrum and Saints were starting to ship some costly penalties.
But Saracens were to give away one of their own, presenting Myler with a tough chance out wide.
It was one he accepted, landing the kick with aplomb to earn a five-point lead with three minutes to go.
Saracens managed to turn the ball over with 20 seconds to go, but, bizarrely, Mordt booted the ball out, ending the game, to the annoyance of his team-mates.
Meanwhile, Saints celebrated as they had secured a priceless win on the road.
Saracens: Goode; Ellery (Bosch 62), Taylor, Barritt (c), Wyles; Mordt, Spencer (De Kock 68); Barrington, George, Du Plessis (Figallo 50); Smith, Hamilton; Rhodes, Brown (Burger 47), Wray.
Replacements not used: Saunders, Thompson-Stringer, Low, Earle.
Saints: Foden; K Pisi, G Pisi, Burrell, Collins; Myler, Dickson (c) (Kessell 74); A Waller (E Waller 65), Haywood (Marshall 79), Brookes (Hill 56); Lawes (Craig 34), Matfield (Dickinson 68); Gibson, Wood, Harrison.
Replacements not used: Hanrahan, Mallinder.
Referee: Thomas Foley