The 28-year old has effectively signed a contract that will ensure he sees out his career playing at the new Langtree Park stadium for Saints.
Wilkin made his Saints debut as an 18-year old having signed from Hull KR. He made his debut in the Saints shirt against Batley in 2003, and has since gone make 231 appearances and score 74 tries. He has won four Challenge Cups and one Super League Grand Final in 2006 during his time at St Helens.
Wilkin said: “It’s fantastic to pledge myself to St. Helens for the next four seasons. I’ve had an amazing ten years with them to date and am really looking forward to more success with them.
“We are all excited about the new season ahead at our new home, Langtree Park. There is a real sense of expectation in the squad.”