Backing up the 12-9 win at Exeter in Round 18, the result keeps Tigers in second place in the league table with just three rounds remaining.
Now the focus switches to a Heineken Cup quarter-final with Toulon in the south of France next Sunday afternoon.
"To come to Northampton and win like that is very important," said Tuilagi who now has seven tries in 15 club appearances this season.
"This is such a tough place to come and win, and also a massive occasion as a Leicester-Northampton derby.
"We got a bit more ball in the backs than we did last week and we're pretty happy about that. It opened up a bit in the second half and as a back that's what you want, to get some space and get the ball. The forwards were massive for us too. They fronted up well and took them on.
"We'll enjoy this for now, but then on Monday we have to start preparing or Toulon.
"This is going to be a massive game and it's very important for us to keep the momentum going. We wanted to win today and it is a good win but we have got to keep working hard and turn it up a bit more next week for Toulon."