Saints will face a trip to Bath in the semi-finals of the Anglo-Welsh Cup.
The black, green and gold progressed to the final four as bottom seeds, with Exeter Chiefs and Newcastle Falcons having scored more tries and Bath accruing more points.
That means Bath get a home tie, along with Exeter, who will host Newcastle.
Saints finished top of Pool 3 thanks to three wins from their four matches, the most recent of which was against Harlequins at Franklin's Gardens last Friday night.
Northampton travel to Bath in the Aviva Premiership this Friday and they will be back there on Friday, March 9 (kick-off 7.45pm) for the cup clash.
Exeter host Newcastle in the other semi-final on Sunday, March 11 (kick-off 1pm).
The final will be at Kingsholm on Sunday, March 18.