The club has moved quickly to tie hot prospect Jonathan to a new deal after the 19 year-old made a big impression in his seven substitute appearances last season.
On committing to the Tigers Jonathan said: “I always wanted to stay at the Tigers. It is where I have worked so hard through the academy ranks to earn my place in the first team and it is where I feel I can also meet my ambitions of playing for England.
“The interest from others clubs was very flattering, but I know this is a place where I can develop to my full potential. Playing for this club is where my heart is.”
Tigers’ head coach Terry Matterson said: “Jonny’s signing is a huge coup for the club. He was very heavily sought after and to have finally tied him up for at least the next two years is a massive boost for the Castleford Tigers.
“In his Super League appearances at the back end of the season he showed everyone what he is capable of. He has all the attributes to play at the highest level and I look forward to helping him achieve this.”
Tigers’ head of youth development Steve Gill said: “It is always good news to know that youngsters who have come through the ranks at the Tigers want to commit their future to the Club.
“Jonny has had to work very hard to get where he is now. He is an example of what can be achieved when you apply a great attitude towards training and playing.”
Walker is one of ten players in the Tigers first team squad set to start the season with Super League experience having emerged through the ranks at The Jungle.