A summer signing in 2011, wing/full-back Morris scored two tries on his Tigers debut against Exeter Chiefs on the opening day of the 2011/12 season and now has seven tries in 26 appearances for the club, including two in last Saturday’s Aviva Premiership victory at London Irish.
Richard Cockerill, Tigers director of rugby, said: “Niall made a big decision to leave Ireland and come to Leicester last summer and he has been been a very important member of the squad here for the last two seasons.
“He has been improving the whole time with us. He is a good young player who is developing really well and doing a good job for us.”
The 24-year-old Morris previously played with Blackrock College and Leinster in Ireland before moving to Welford Road.
Morris said: “I’m really enjoying my rugby at Leicester and I was happy to agree a contract extension.
“I think I’ve improved a lot as a player with Tigers and that is something I want to continue to do here.
“I’ve had great support from the coaches and the players, and I want to continue to play here and do my best for the club.”