Northampton extended their year-long unbeaten home run and avenged their Premiership defeat away to last season’s beaten finalists Leicester three weeks ago.
Malelili Satala’s first senior try gave Leicester an ideal start but that was as good as it got for the in-form Tigers at a sold-out Franklin’s Gardens.
Nineteen-year-old back-row Henry Pollock responded as the much-changed East Midlands rivals traded early scores, and the Saints did not look back as they clicked into gear.
James Ramm put them ahead before centre Tom Litchfield finished a slick backs move to make it 19-7 at the interval.
Pollock teed up George Hendy for Northampton’s bonus-point try and academy product Ewan Baker underlined an impressive night for the young Saints before Will Wand gave Tigers the final say.
In the other Midlands tie in Pool B, Championship leaders Coventry extended their 100 per cent start to the season away to second-tier rivals Nottingham.
Matt Arden booted the hosts into the lead, but Charlie Robson and Matt Johnson scores put the visitors 12-3 up at the break.
Ryan Olowofela cut the deficit to two points, but Ryan Hutler, Jordan Poole, David Opoku and Will Lane secured a bonus-point win despite Jay Ecclesfield’s consolation score.
Fixtures
Saturday
Pool A: Caldy v Newcastle Falcons (14:00 GMT)
Pool C: London Scottish v Harlequins (14:00); Ealing Trailfinders v Saracens (15:00)
Pool D: Ampthill v Bath (13:30); Bristol v Bedford Blues (15:00)
Pool E: Hartpury RFC v Gloucester (14:30)
