France midfielder Schneiderlin was unable to break into Jose Mourinho's first-team plans at Old Trafford, playing just 11 minutes in the Premier League across three last-gasp substitute appearances.
He is the second player to join the Toffees this month, following former Charlton youngster Ademola Lookman in moving to Goodison Park, and links up with Ronald Koeman again after the pair previously worked together at Southampton.
Mourinho said of his impending exit this week: "I'm sad and I'm happy. I'm sad because I like him and he could be an option for us in a long season. I'm happy because this is what he wants, he wants to play every game and wants to be an important player in the team.
Thanks to all the fans for your support I wish you all the best for the future ! pic.twitter.com/Insa1xAp1s— Morgan Schneiderlin (@SchneiderlinMo4) January 12, 2017
"If this is what he wants I'm happy for a very good professional and someone that I can only say good things about."
Schneiderlin told Everton's official website: "Everton is a big club in the history of English football. I've always loved the atmosphere in the stadium.
"I've always liked playing here. I can't wait to play and to represent this great club.
"There is a manager in place here that I know, I know he can get the best out of me, I know his style and how he likes to play football. He was very good with me from the start and I enjoyed playing football under him.
"When I spoke with the manager and the people in place at Everton I understood immediately that they have a very good plan for the future of the football club.
"I just want to play football. I want to put my print on this club and do everything to get Everton where it belongs."