Harrison came through the Tigers Academy ranks after playing his early rugby with John Cleveland College and Hinckley RFC, and has now firmly established himself in the club’s first-team squad.
Capped at Under-20 level by England, Harrison passed the 20-game mark for first-team appearances during February and he has been a regular in the matchday squad throughout the 2011/12 campaign.
Director of rugby Richard Cockerill said: “Sam is a good young English talent who has come through the ranks here, starting with the Academy and learning his trade along the way.
“He’s had as much game-time this season as many of our senior players, he is developing as a player all the time and we’re delighted that he wants to stay.
“He is a very good young player in a very competitive position and he has put his hand up in terms of selection with his consistent form this season.”
Harrison said: “This is the club I always wanted to play for and it’s a privilege being able to train and play alongside so many top players.
“When you come here you know all about the players who have worn the Tigers shirt before you and the standards that are expected when you wear the shirt.
“I’ve particularly enjoyed having a run of games this season because that helps your confidence and your game. I’m very happy to agree a new contract with the club.”