The 26-year-old had a year remaining on the contract he signed after moving from Wakefield in 2015, but has now signed on for two more seasons.
McShane, who has also had spells on loan at Hull and Widnes Vikings, was ever-present for Tigers this year, scoring seven tries in 32 appearances.
“It’s a big thing for my family to be re-signing with the Tigers,” McShane said.
“My wife loves it at this club and that makes it a lot easier for me.
“From day one, coming in midway through last year, I knew it was a club that was for me.
“The way people are around here is great.”
“You come in every day with a group of good people and all they want to do is make you better and that’s throughout the coaches, players and everyone else at the club.
“Then you come to game day and you’ve got the fans. When you come to training sometimes at 7 or 8 in the morning you’re guaranteed to see a couple of Cas shirts walking round the streets and to have fans like that who back you as a team that much, it’s just something I want to be a part of.”
Tigers coach, Daryl Powell believes McShane has the potential to play for England.
“Paul McShane has always been a very good player, but I thought we started to see how good he can really be towards the middle and back end of last season,” Powell said.
“He is a natural ball player who understands the game very well. I have no doubt he is going to improve and although he has a host of competition at international level, I think he is one of the most natural hookers in rugby league and should strive to attain that level.
“I look forward to working with him during his extended contract and I’m delighted he wants to stay at the Tigers.”
Tigers chief executive Steve Gill said: “Paul has become one of the fans’ favourites and has been a key figure in our squad since joining us from Wakefield.
“I’m really pleased he has committed to the Tigers for a further two years.”