The New Zealander has committed his future to the Franklin's Gardens outfit until at least 2010, and he will be a key figure on their anticipated return to the Guinness Premiership from National League One next season.
Reihana, who joined Northampton from Waikato midway through the 2002/03 campaign, has scored more than 700 points, including 49 tries, in 141 appearances for Saints.
He said: "I wanted to stay here and help get the club back to where it should be.
"If we get back into the Premiership, it will be a massive challenge to stay there. I am looking forward to it."