Puletua, 31, joined Saints from Penrith Panthers and is in his third season at the club.
He said: “I’m absolutely thrilled to be seeing out my career at the Saints. They are the only Super League club that I would consider playing for and I’ve enjoyed every aspect of my time here so far, particularly the fans who have been absolutely amazing to me.
“With the new stadium near to completion, and some new international signings to complement a great crop of young players coming through, the next couple of years are going to be more than exciting for Saints players and fans alike.”
Saints have already lost half-back Kyle Eastmond to rugby union and prop James Graham to Canterbury Bulldogs, but have countered this with the signing of Kiwi international Lance Hohaia and forward Anthony Laffranchi, and now the retention of Puletua.
Coach Royce Simmons added: “This is a great lift for us all. Tony is a rare breed of forward who combines size with athleticism and skill and can play both back and front row.
“He brings an extra dimension to our game and has been in great form of late. He is in prime physical condition and there is no doubt that he can play on at the highest level for another couple of seasons after this.”