The German will effectively replace departing sprinter Mark Cavendish and will ride alongside exciting young Colombian fastman Fernando Gaviria in 2016.
Kittel suffered a torrid 2015 season, with an illness picked up after the Tour Down Under hampering his early-season schedule.
Having won eight stages of the Tour de France between 2013 and 2014, he was left out of Giant's squad for this year's race in favour of John Degenkolb. He was also omitted from their Vuelta squad as well as Germany's team for the World Championships.
"I want to thank the team for the faith they've put in me, and that they will support me in this new chapter of my career," Kittel said. "I am looking forward to the new challenges of Etixx-Quick Step, a team, I consider as one of the best teams in the world.
He added: "I am also happy that I have a few friends on this team already, including Tony Martin. Tony is one of my best friends in cycling. We rode together when we were younger, and I can't wait to do it again at the professional level."
Etixx-Quick Step CEO Patrick Lefevere said: "As a team we will do our best to put him in the right condition, building a group of riders around him. He showed his potential in just a few years time, with dominating performances among his palmares."
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