Cairney signs a three-and-a-half year deal at Ewood Park from Premier League outfit Hull City, and has caught the eye with a series of impressive performances in midfield.
The 22-year-old has scored twice in 24 appearances for Gary Bowyer's men, and was delighted to make his move permanent.
He told the club's official website: "I'm very pleased to sign permanently - that was a goal of mine when I came on loan in August.
"First and foremost, I wanted to try and get games under my belt. I knew it was a big club, with a lot of good players here and I really wanted to try and do my best and help the team push on.
"I feel like I've played well this season, but I still think there's more to come and I'm looking forward to the future with Blackburn Rovers."
Meanwhile, 25-year-old striker Gestede also pens a deal until 2017, having originally joined Rovers in a loan switch from Cardiff City in November.
The Benin international scored his first goal for the club in the 2-1 victory over Leeds United on New Year's Day, and he is looking forward to attempting a push for the play-offs.
"I am very happy to sign for Blackburn Rovers," he said. "They gave me the chance to play and to be on the pitch and now they have given me the chance to sign a permanent deal and I'm delighted to take it.
"I trust in my team-mates and we are very close to the play-off places, so if we keep playing like we have and keep believing in ourselves, we can do something."
