Since turning pro in 2007, the 31-year-old Belarusian has claimed numerous stage wins – the highest profile of which came in the 2008 and 2011 editions of the Giro d’Italia.
The three-time national time-trial champion also wrapped up the overall title at the Route du Sud in 2011 and this year claimed the bronze medal at the World Time Trial Championships in Limburg.
Kiryienka said: “I am very happy to be joining Team Sky and I’m confident I will fit in without any difficulty as there are people I've known for a long time in the squad.
"Team Sky have enjoyed a fantastic season in 2012 and I’m looking forward to contributing towards even greater success over the next three years, whether that means working for myself, or for someone else.
"With the help of Team Sky I want to continue developing as a rider. Everyone has made me feel welcome and I am keen to getting started.”
Sports director Nicolas Portal believes the signing will improve the team and see the rider go from strength to strength.
"Vasil has won some big races and put in some impressive performances at the very highest level,” Portal said. “His stage win at the Giro d’Italia last season was phenomenal, and we were all impressed with the way he was able to battle on and take the victory.
"He was third at the world time-trial championships and has a lot of other victories to his name. He’s such a strong rider and is going to be a great signing for the team.
"He can perform very highly in his own right, or in a team capacity, and we know what he is capable of. It puts us in even better shape heading into the big tours of 2013.”