Nic Groom grabbed two late tries on his debut but Saints suffered an 18-14 opening-day shock as Bath won at Franklin’s Gardens for the first time in more than 16 years.
George Ford landed all 18 points for the away side, who started life under new boss Todd Blackadder with a first triumph in Northampton since April, 2000.
For Saints it was another disappointing start to an Aviva Premiership campaign, following last year’s defeat to Worcester Warriors in the curtain raiser at Sixways.
Jim Mallinder’s men had sent fans flowing towards the exits after going 18-0 down with 10 minutes to go, but a brace from South African scrum-half Groom gave them hope.
However, with just a minute remaining after Stephen Myler had landed his second conversion, the ball was knocked on, Bath got the scrum and kicked the ball out.
That meant it was a happy first return to the Gardens for Samoan scrum-half Kahn Fotuali’i, who joined Bath from Saints during the summer.
Fotuali’i’s first act in the match hadf been to kick the ball out on the full, bringing loud cheers from the home fans, who gave their former star a warm welcome.
That error gave Saints possession and they used it to continually knock on the Bath door, relentlessly probing for an opening, with debutant Louis Picamoles leading the charge.
The away side stood tall against the pressure, but they were hit with a big injury blow just 13 minutes in as Wales No.8 Taulupe Faletau was forced off on his debut.
Saints had the chance to go ahead 10 minutes later, but Harry Mallinder’s ambitious penalty attempt from close to halfway went to the right of the posts.
Bath earned a penalty at the other end eight minutes before the break and fly-half Ford, who had hit the post with a drop goal, landed the kick from the tee to put his team ahead.
Bath were eager to take points from every visit to the Saints half, and Ford attempted another drop goal, which he landed with aplomb.
The players headed off the field for half-time amid a subdued atmosphere, with little spark shown during the opening 40 minutes.
It had all been a bit last season for Saints, who were struggling to come up with ways to break down the opposition in wet and windy conditions.
And Bath were making them pay, with Ford landing a penalty four minutes into the second period.
Saints had been 14-0 down at half-time against Bath at the Gardens back in April and, at 9-0 down on this occasion, they needed a similar stirring comeback.
But Bath were playing a clever game, soaking up the pressure and breaking when they had the chance, with Semesa Rokoduguni giving them a get-out clause.
Saints were desperate for some impetus and threw on two of last season’s stars, Paul Hill and Teimana Harrison, in a bid to lift intensity levels.
Myler was also added to the mix soon after, pushing Mallinder to the centre alongside Luther Burrell, who had led the team out on his 100th Saints appearance, but still there was little threat.
And Bath soon had another three points as Ford slotted his second drop goal of the afternoon, to the dismay of the frustrated home fans.
The game was drifting away and it was soon out of reach as Ford landed another penalty with 15 minutes to go.
The 15-point deficit didn’t look like being narrowed and instead it was the away side who played the game in the opposition half, sensing their long-awaited win was coming.
In truth, there was only one team looking likely to register points and Bath had three more through yet another Ford penalty.
Some home fans headed for the exits with more than 10 minutes of the match remaining and it was all growing ever more disappointing for those of a Northampton persuasion.
Saints did finally put some pressure on and Bath scrum-half Chris Cook paid the price as he was sent to the sin bin for the last seven minutes of the game.
Groom, on for Lee Dickson, scored almost immediately and Myler converted, giving Saints a sniff of a bonus point.
And when Groom scored again two minutes before the end, with Myler again converting, there was a chance of a remarkable comeback.
But a knock-on close to halfway ended hopes of a miracle comeback and Bath were steady in the scrum before kicking the ball out to secure a fine win.
Saints: Foden (North 38); K Pisi, G Pisi (Myler 57), Burrell, Tuala; Mallinder, Dickson (Groom 66); A Waller (Ma’afu 62), Hartley (Clare 66), Brookes (Hill 52); Lawes, Paterson (Dickinson 71); Wood (c), Gibson (Harrison 52), Picamoles.
Bath: Homer; Rokoduguni, Joseph, Clark, Banahan (Williams 66); Ford, Fotuali’i (Cook 66); Catt (Auterac 65), Batty (Dunn 65), Thomas (Palma-Newport 65); Ewels, Attwood; Garvey (Sisi 62), (c), Denton (Priestland 73), Faletau (Ellis 13).
Referee: JP Doyle