The 21-year-old Scotland international has signed a new five-year deal, which will keep him at Ewood Park until June 2018.
A product of the club’s Academy, Grant has been with Rovers since the age of 16, quickly progressing through the Reserves and into the senior squad.
Since making his debut as an 18-year-old against Aston Villa on the final day of the 2009-10 season, Grant has blossomed into one of the brightest prospects at the club.
Last season saw him form a formidable partnership with captain Scott Dann at the heart of the Rovers defence – impressive performances at club level leading to a competitive Scotland debut in March, in which he scored in a World Cup qualifier against Wales.
Grant said: “As soon as the end of the season came and I heard that the club wanted me to sign a new deal, I couldn’t wait to get it done and it feels brilliant.
“I’ve been at the club for a while now, it’s a great club and I’m really happy to extend my stay here.”
Rovers manager Gary Bowyer, who has worked with Grant since youth level, said: “First and foremost, this is fantastic news for the football club.
“It is vitally important that we keep hold of our young, home-grown talent, who the supporters can identify with.
“I have been delighted with Grant’s progress from the youth team to the first team and this new contract is richly deserved after a superb season for the club.
“He epitomises what we are about – hard working, committed to the cause and a player who is prepared to put his body on the line.
“It is a great boost for everyone connected with the club and especially Grant, who will be looking to kick on further next season.”