"It's been a great experience to be a part of the first team regularly in 2011 and I've been learning a lot," he said.
"I'd certainly like to thank the coaches, especially Dorian West, for taking the time to help me develop as a player and for having the faith in me to give me regular game time.
"There was no hesitation in signing again at the Saints. I've come through the system here and it is somewhere where I feel very at home. I know I'm still young as a prop and that there is plenty left to learn and I hope I can improve a lot over the next few seasons."
Prescott, 32, joined the Saints in December. Named in the Championship Team of the Year in 2009/10, the tight-head specialist arrived at Franklin's Gardens after a brief spell at Leinster. He has also played for Glasgow Warriors.
"I've only been at the club for a short time but I've been made to feel very welcome," Prescott commented. "It was a great opportunity to be offered the chance to be a part of such a great squad of players and I had no hesitation in signing again," said Prescott.
Director of rugby Jim Mallinder said that the contract extensions represented both sides of what the Saints squad needs going forward.
"Alex is a player with massive potential at the start of his career while Ben gives us plenty of experience in a crucial position," he said.
"We need both types of player if we want a successful squad, young players who are hungry to improve and develop and experienced players who can pass on their expertise. Most importantly we want players who are committed to help the club achieve and continue our recent development, and both Alex and Ben fit into that group.
"I'm very happy that they have signed new contracts with us."