The 33-year-old, who was an outstanding performer on both the 1997 and 2001 Lions tours, joined the Franklin's Gardens team in 2001 and has now extended his stay until 2007.
Saints acting head coach Budge Pountney believes the re-signing of his former international team-mate will be a key factor for the future of the club.
Pountney said: 'Tom is of the highest pedigree of front row forwards and we are extremely pleased that he has decided to stay at Northampton.
'He has a pivotal role in the development of this team and we believe that with his experience, we can move onwards to better things.'
Northampton operations director John Steele added: "Tom has given tremendous service to the club during the last three years.
'He has been one of the most consistent performers in elite rugby and his record speaks for itself.
'We are delighted he has committed himself to the Gardens as I am sure we will be seeing some of his best rugby during the next two years.'