An impressive Saints performance snapped a run of two straight defeats, and the hosts will have been disappointed not to take a bonus point such was their dominance.
Lee Dickson, George Pisi and Phil Dowson crossed for the hosts with the boot of Ryan Lamb also adding 15 points, while Ernst Joubert popped up with Sarries' consolation try late on.
Saracens had no answer to the Saints' first-half onslaught and the game was as good as over as a contest by half-time with the hosts leading 27-3.
Yet it was Saracens who could have taken the lead as early as the third minute, a pass from Alex Goode sending David Strettle on a 40-metre run but the wing was hauled down short of the line.
The visitors continued to hold their own in the early play but it was the Saints who opened the scoring in the ninth minute. Ben Foden began the move by beating two players in his own 22 and it ended with Dickson crashing over for a try which Lamb converted.
Saracens got on the scoresheet when Owen Farrell kicked a 30-metre penalty, although that was soon nullified by one from Lamb.
Saints then produced another movement of excellent quality with Dickson, Roger Wilson and Chris Ashton combining, and but for a wayward pass by Lamb Northampton would have extended their lead.
Saints collected their second try after 20 minutes when Pisi burst through some weak tackling to run 30 metres and score a try which Lamb converted.
Farrell missed a penalty before Lamb fired over a 30-metre drop goal to give his side a healthy 20-3 lead.
Ferocious tackling from the hosts prevented the Saracens from building up any momentum and it was no surprise when Northampton extended their lead, Dowson driving over and Lamb converting.
Saracens' woes continued after the break when Lamb kicked his second penalty after 55 minutes.
Northampton relaxed by taking off star players Dickson, Lamb and Courtney Lawes, allowing Sarries to make it more of an even contest.
The visitors could have had some reward for their efforts but chose not to take kickable penalties in favour of more attacking options.
Apart from one powerful burst from John Smit they never looked like scoring a try until the last movement of the game when Joubert crossed following a strong run from Chris Wyles.
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