The 24-year-old has spent his whole professional career to date with the Belgian squad, but moves across to the British outfit to play a part in the Belgian Classics campaign and stage races throughout the year.
Wisniowski will join after a successful season, winning a stage at the Tour de San Luis and finishing second overall at Driedaagse van West-Vlaanderen.
“I’m really happy to be joining Team Sky. It will be nice to be a part of the team in the Belgian Classics and maybe even in the Grand Tours,” he said.
“The team is really, really strong. There are so many good riders and I think I can learn a lot with the team. It will be a great experience for me to be on the same team as riders like Chris Froome and Michal Kwiatkowski.
“It’s also great to be joining two fellow Polish riders, Michal Golas and Kwiato. We are friends, we always train together, and it will be nice to be in the same team again.
“When we were at Etixx we’d train together, and even now that we’re on different teams, we still train together most of the time.”
Wisniowski becomes Team Sky’s third official signing of the year, joining British duo Owain Doull and Tao Geoghegan Hart at the team for next season.