The popular Australian second-row, 31, has been with the Tigers since joining from Cronulla Sharks ahead of the 2017 season.
A big fans favourite given not only his all-action style on the pitch but positivity off it, he has helped the club reach both the Super League Grand Final and the Challenge Cup Final, as well as lift the League Leaders’ Shield.
Sene-Lefao played his 100th Super League game in Saturday’s Magic Weekend win over Salford Red Devils which firmly keeps them on course for the play-offs.
Having lost against St Helens at Wembley in July and fell versus Leeds Rhinos in the 2017 Grand Final, the forward hopes to push on and return to prove victorious at Old Trafford.
“To get the trophy at the end would mean the world,” he said.
“All the hard work that we’ve put in for the last five years would show.
“Making that final for Wembley was awesome in itself. “Obviously, we didn’t get the trophy that day but man, what a journey it was just to even get there in the things we had to overcome.
“There is another trophy at hand now; that’s the main focus at the moment.
“Everything else will look after itself.”
Sene-Lefao added: “There are not many words that I can say that would show my appreciation for the club itself and what I’ve achieved over here.
“Every moment is special and there is definitely pride in the jersey that I wear every week, that is something I’m going to miss.
“I could never think five years ago that I would be here still and playing for Cas, such a beautiful town, and the people here, the support has been awesome.
“It is sad to say that the time is up but when one door closes, another door opens and it’s another opportunity for me and I’m excited for that.
“But our season isn’t finished. I’m looking forward to the next couple of games.”
Castleford head coach Daryl Powell added: “Jesse is such a bundle of energy - the fans love him because of who he is and the way he goes about things.
“He’s a very religious man. I ask him to say a prayer for us every now and then depending on what’s happening.
“He has been a quality player for us; 2017 was a massive year for him.
“I think he was unbelievable that year and he’s consistently been in our team as a back-rower since.
“A real strong player and as a personality he is a really great family man who does everything he can for his family.
“In and around the community he is hugely respected, and he will be very fondly remembered by everybody.”