Wilkin, 33, who moved to Saints in 2002 and has won seven trophies since then, has agreed a two-year deal.
Former Leeds and Wakefield forward Amor, 29, helped Saints win the Grand Final in his 2014 debut season and has now signed a three-year deal.
"I'm delighted that both players have agreed to stay at the club," said head coach Keiron Cunningham.
"They are integral to what we do here and provide leadership and professionalism to the younger players in the group."
St Helens captain Jon Wilkin and prop Kyle Amor have signed new contracts with the Super League side.