"Everyone here is delighted that Tom has signed a new contract," said Richard Cockerill the Tigers' director of rugby.
"He came through our Academy and is now a top-class player. He really wanted to stay, the club really wanted him to stay and we're very happy that the details have been agreed and he has signed.
"Crofty had to work really hard when he came into the squad as a youngster and he was determined to have a real crack it his rugby. He epitomises the spirit of the club and he is already seen as a senior player at a relatively young age.
"He is another example of how well players can develop within our environment. He proves what hard work and determination can do in the game and that sets a great example for other young players.
"He is not new on the international scene but he is now being talked about as a world-class player at the very top end of the game. And, at 25, he can get even better.
"His decision to re-sign shows that we can hold on to our players. It's not just about money, it's about playing for the club you love and Tom appreciates this is a good environment to work in and improve in."