The 21-year old Scotland defender has committed himself to the Ewood Park club after initially arriving from Rangers as a teenager in 2008.
"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," he said.
"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." Manager Gary Bowyer added: "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."