The reigning Steve Prescott Man of Steel - who made his England debut against the Combined Nations All Stars a week ago - was already under contract for 2022 but has now signed an improved deal for next season and a three-year extension on top.
The news will delight Castleford's fans given he has been such a crowd favourite and integral part of their squad since Daryl Powell signed him from Wakefield Trinity in 2015, developing into one of Super League's finest players.
It will also end speculation that the 31-year-old McShane would follow his head coach to Warrington Wolves next term as team-mates Oli Holmes and Pete Mata'utia are doing.
“I’m over the moon to be staying for the next four years,” said the ex-Leeds Rhinos hooker, who was ever-present when Castleford won the League Leaders’ Shield and reached the Grand Final in 2017.
“I have to give credit to Cas for improving next year’s deal for me as well which is something they didn’t have to do and something that I’m grateful for.
“I want to keep getting better at everything I do. Hopefully in the next four years, it sees me keep improving.
“I feel great; I feel as though the older I get, the smarter I’m getting both playing-wise and body-wise in looking after myself.
“The club has made me the player that I am now - the people involved - and my kids only know me playing for Cas which is a big factor as well.
“I’ve probably turned from a boy to a man here.”
Leeds-born McShane, who hopes to help Castleford win the Challenge Cup at Wembley in just over a fortnight’s time and will be 35 when his new contract ends, has flourished under Powell.
“He has been someone who has been that driving force in me getting better,” said McShane.
“Every year he is wanting me to keep improving and keep pushing.
“As a man, I’ve got so much respect for him, the time and effort that he has put into me.
“Sometimes I needed a cuddle, sometimes I needed a rocket up me: he knew the right times to do those things.”
Powell said: “Paul has been such a pivotal figure ever since he came to the club, but he has grown in every aspect of his performance levels, and his professionalism is a real driver for the team.
“He is a class fella, and I am delighted he has agreed to stay at Castleford; the club means so much to him and he means so much to the team.”
Lee Radford takes over as head coach at the end of the season and he said: “To have Paul long-term is a credit to the club really and a credit to him.
“He is arguably one of the most influential players in any team in the competition; he seems to be getting better with age.
“I was fortunate enough to get to play with him at Hull when he came on loan from Leeds, formed a good relationship with him there and hopefully we can continue that in a coach and playing capacity.
“I think he is the most influential No9 in the comp, how he steers the team around and how he takes the pressure off the pivots, and his leadership qualities are there to see.”