The England centre, currently in Hong Kong with the British and Irish Lions, has scored 19 tries in 62 appearances for the club since making his mark during the 2010-11 season.
"Manu is a world-class talent and has taken every challenge that has come his way in his stride in the last three years as a senior player," said Tigers director of rugby Richard Cockerill.
"We all know what he can do, but he is maturing as a player all the time too which means he is getting better and better with every season.
"He was very proud to have the opportunity to follow his brothers into the Leicester Tigers team.
"Leicester is his home and we're delighted that he has committed his long-term future to the club."
The 22-year-old still had a year left to run on his previous deal but Leicester, who have not disclosed the exact length of the new contract, have moved to secure Tuilagi's future.
The Samoa-born three-quarter secured his first Premiership winners' medal last weekend, scoring a try in Leicester's Twickenham success over Northampton.
Tuilagi is the fifth member of his family to represent the Tigers, with elder brothers Fereti, Henry, Alesana and Andy also having played for the Welford Road side.
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- Leicester Tigers