David Ribbans reflected on a 'massive' success after Saints won at Welford Road for the third time in a row.
Second row forward Ribbans scored two first-half tries to help his team into a 14-10 lead at the break.
But Leicester Tigers battled back and were 22-14 up before scores from Tom Collins and Fraser Dingwall earned Saints the derby-day spoils.
It did not enable them to progress from their Premiership Rugby Cup pool, as they had lost their opening three matches in the competition, but they do now have some momentum to take into the Gallagher Premiership opener at Saracens next Saturday.
And Ribbans said: "It was massive.
"My tries were a bit lucky, they were some set-piece moves we worked on and they worked on this occasion.
"Tayls (Henry Taylor) will take the credit for that (first try), but it was something we'd been working on and it finally paid off, four weeks later. I'm happy about that.
"To get a win here is massive and coming off the last few weeks, we knew how big it would be to get a win.
"We're really stoked about it."
And he added: "It's a cool place to play, derby day and a good crowd, a hostile Leicester crowd so it was massive to get the win.
"We made it hard for ourselves but it was great to get the victory - very important."
Saints did not win at Tigers between February 2007 and April 2018, but they have now won three successive matches at Welford Road.
And Ribbans, who arrived in Northampton during the winter of 2017, said: "I didn't know much about that history but it's great that as a young group we've got the edge over Leicester at the moment.
"Hopefully we can do that in the league."