Worcester cast aside their dismal league form to register a decisive victory in their opening EDF Energy Cup tie.
Gavin Quinnell, brother of former Wales forwards Scott and Craig, led the Warriors' assault on Anglo-Welsh silverware by bulldozing his way over for a brace of tries.
It marked a memorable full debut for the powerful 22-year-old back row, who was substituted in the 52nd minute, after arriving from Llanelli over the summer.
Warriors fly-half James Brown contributed 14 points to help his side to a morale-boosting win following four straight Guinness Premiership defeats.
Only Chris Horsman remained from the side beaten by Bath last weekend, with director of rugby John Brain giving his fringe players a chance.
Worcester controlled the first half and fully deserved their 18-0 interval lead, which would have been greater still had they been a little more ruthless.
In contrast Northampton, missing Kiwi fly-half Carlos Spencer through injury and showing seven changes, were rudderless and squandered the few opportunities they had.
Dylan Hartley and Mark Robinson touched down in a marginally improved second-half display but with Robbie Kydd enduring an off day with the boot, the home side never looked capable of releasing Worcester's stranglehold on the game - even when sin-binnings had reduced them to 13 men.
The Warriors now have a fine chance of qualifying for the knockout stages of the cup with Sixways hosting their remaining Pool D fixtures against Leicester and the Dragons.
They made an impressive start with Quinnell crossing from a line-out catch and drive, initiated when they opted to send a kickable penalty into touch.
James Brown converted but the Warriors were soon under pressure themselves and would have conceded but for handling errors from Ben Cohen and Chris Wyles at crucial moments.
A superb pass out of the tackle from Quinnell to Ben Gotting began a promising move for the visitors but the hooker then opted to ignore a clear overlap and go it alone - to little effect.
Worcester wasted another points-scoring opportunity when Brown fired a simple drop goal wide but the visitors managed to extend their lead in the 28th minute.
The Warriors' pack was punching holes in Northampton's defence with Quinnell delivering the killer blow down a tight blindside for his second try.
Brown missed the conversion but slotted two penalties to give Worcester an 18-0 lead two minutes short of the interval.
Northampton raced out of the blocks for the second half and made the breakthrough when a spell of sustained pressure was concluded when substitute Hartley barged over in the right corner.
Saints' hopes of continuing their fightback suffered a setback when skipper David Quinlan was shown a dubious yellow card for tackling off the ball.
Brown punished the infringement by kicking the three points and then added his fourth penalty to leave Northampton dead and buried.
Worcester were reduced to 13 men when Miguel Avramovic and substitute Drew Hickey was sin-binned in quick succession but Saints could not take advantage thanks to a raft of turnovers.
Uncontested scrums followed with injury forcing Worcester to play two hookers in the front row but the outcome had already been decided, despite Robinson's late try.