Saints will meet Saracens in the Aviva Premiership final after Mark McCall’s men outgunned Harlequins at Allianz Park on Saturday.
Sarries recovered from 17-11 down to earn a 31-17 play-off semi-final success and book their place at Twickenham on May 31.
Saints had cemented their place in the showpiece with a thrilling 21-20 victory against local rivals Leicester Tigers at Franklin’s Gardens on Friday night.
Tom Wood’s try two minutes from time meant Jim Mallinder’s men progressed to the final.
And it will now be a battle of the regular season top two, with table-toppers Sarries facing second-placed Saints.
The teams have met four times in all competitions this season, with Saints winning the home league game 41-20 and earning two LV= Cup victories.
But Saracens won the most recent meeting between the teams, claiming a 28-24 win at Allianz Park in April.
Both teams will first have to contend with European finals first as they head to Cardiff next weekend.
Saints scrap it out with Bath in the Amlin Challenge Cup final on Friday, before Saracens face Toulon in the Heineken Cup showpiece a day later.