Klavan was unveiled to the local media this morning.
He said, "Cagliari was the best possible choice, despite other proposals.
"It was the best option, after hearing from friends I know and who played in Serie A. I'm ready to debut.
"I've always had the desire to play in Serie A, one of the best leagues in the world. I was lucky to be able to play in the big European leagues, this is another big challenge for me.
"The operation was born and ended within two days.
"I grew up with the model of Paolo Maldini who was always very calm with the ball between his feet: this is my style of play. I chose number 15 because I have always had this number in the national team."