Contador, who previously triumphed at the Tour in 2007 and 2009, says he will be targeting a third Tour de France victory.
The 33-year-old, who has won all three Grand Tours and finished fourth in the Vuelta last week, has spent five years with the Tinkoff outfit that will leave the WorldTour at the end of this season.
"I am thrilled about the opportunity that is in front of me. Trek-Segafredo is a very attractive and ambitious project that really inspires me," Contador said.
"I had some excellent conversations with the team management and we have a lot of goals and priorities in common. The big objective is to try and win the most important races on the calendar, first and foremost the Tour de France."
Contador will also take trusted lieutenant Jesús Hernández and sports director Steven de Jongh along with him to the team.
“I am really happy to come back to Trek because I also rode a Trek bike in 2009," Hernandez said. Alberto is like my brother and coming back with him to the Trek family is really something special. It means a lot to me.
“2017 will bring once again a new experience and so I am really looking forward to starting the next season with renewed ambition.
"Obviously, my main ambition is to support Alberto and the other leaders of the team. When they are happy with my work, I will be happy as well.”
