Northants had two former Worcestershire players to thank for the table-topping victory that earned them a home Twenty Cup quarter-final in late July.
Stephen Peters hit an unbeaten 61 off 52 balls as Northants cruised to a comfortable win with two overs in hand.
Worcestershire (110-9) had earlier been undone by another New Road old boy Andrew Hall, who took 4-19.
Northants replied on 118-3, Peters and Alex Wakely (29no) sharing an unbroken, matchwinning 66-run stand.
Northants had help in earning top spot (and that home quarter-final) from Warwickshire, who denied Somerset's hopes in beating them by just one run at Edgbaston.