The former England back rower should now stay at Saints until the end of the 2016 season.
“This club has been an important part of my life and it is a natural thing for me to extend my contract,” the 31-year-old said.
“I am pleased the club wanted me to do the same.
“I have had some of the best memories of my life here and I’m looking forward to continuing that for the next couple of seasons.
“Being captain is a role I am proud of. My remit is to now highlight and bring through some of the next leaders at the club.
“That can come from players at the early stages or their career, those in their mid or those towards the latter stages. Leadership might not be something they are accustomed to and I am looking forward to developing that.”
Wilkin has won 12 trophies during his time with St Helens. Club chairman Eamonn McManus is delighted that such a highly decorated senior player will be staying on at Langtree Park.
“It’s great news for the entire club that Jon has extended for a further season,” he said.
“As well as a proven player at the highest levels, he is a natural leader and great ambassador. Given the youthful make up of our squad, it’s critical that we have a highly respected, experienced and versatile captain, and Jon is certainly that.
“He’s absolutely committed to the cause and we have a lot to look forward to under his continued leadership.”