The 20-year-old Colombian, in his second pro year with Androni-Sidermec Bottecchia, has nine wins so far this year. In addition to l'Avenir, he has also won two stages each and the overall title in both Sibiu Cycling Tour and the Tour de Savoie Mont Blanc.
He has also brought in top results in bigger races, such as fourth in the Settimana Coppi e Bartali, and ninth overall in the Tour of the Alps.
"With Team Sky providing a successful home for Colombian riders over the years, Bernal will be hoping to continue his rapid development as a next generation GC threat," the team said in a press release.
"I always dreamed of being with this team. I never thought the opportunity to join would come this fast, so to sign for Team Sky is a dream come true," Bernal said.
"My first goal with Team Sky is to learn. I want to learn from my teammates and take advantage of the experience that there is in the team. I'm excited to be joining Team Sky and I want to contribute as much as I can."