The news of the signing came only hours before Kwiatkowski would attempt to defend his 2014 UCI road world championship title in Richmond, Virginia.
"Team Sky aim for the highest goals in cycling so I'm very happy that this move has become a reality," Kwiatkowski said.
"Sir Dave Brailsford believes in my ability, which gives me great confidence for next season, and I know that this team can help me raise my performance levels and win big races.
"The team's marginal gains philosophy really fits my approach to cycling and I have great respect for what this team has achieved in such a short time.
"I am excited and motivated to race for Team Sky next year."
The 25-year-old Polish rider has had a relatively quiet season with Etixx-QuickStep compared to his breakout 2014 year when he seemed to be at the business end of every race he entered.
He still managed to win a spring classic in the Amstel Gold Race and picked up second places at Paris-Nice and the Volta ao Algarve though he abandoned the Tour de France on Stage 17.
"Michał has performed fantastically well over the past couple of years," Team Sky manager Dave Brailsford said. "We have been following his career for a long time. We have attempted to sign him on two occasions previously and weren't going to miss out this time around.
"Team Sky can help him progress and develop both his one-day racing and stage racing. Michał is still young, a great talent for the future, and will keep getting better."