Saints will be at the Singha Premiership Rugby 7s Series finals day at the Ricoh Arena on August 7 after claiming two wins at Franklin’s Gardens on Friday night.
The hosts bounced back from an opening-game loss to Harlequins to defeat Saracens and Gloucester and book their place in the Coventry showpiece.
Saints will now face Exeter Chiefs in the quarter-finals (kick-off 2.25pm) as they bid to return home with the trophy.
They got off to a sluggish start in the pool stages, having gone 12-0 down to Harlequins early on.
Howard Packman and Tom Emery responded with tries, but Quins raced clear and Lewis Ludlam’s late score was only enough to reduce the deficit to 22-19.
And Quins scored again before the end to earn a 29-19 victory.
Saints got off to a much better start in their second game, against Saracens, as Tom Collins scored within two minutes.
Saracens took the lead before Collins scored twice more to complete his hat-trick.
Saracens then roared back to go in front again, but Sam Olver grabbed the winner late on to secure a 24-17 success.
In the final game, Saints grabbed a 27-17 win against Gloucester, with Packman scoring four times and Alex Rayment also registering.