Baines announced his retirement from football at the end of the 2019/2020 season at the age of 35.
The former England defender made nine appearances in all competitions for the Toffees last season but decided to retire despite manager Carlo Ancelotti offering him a one-year contract.
Baines will become Everton’s first professional development coach and will work with the club’s young players in the first team as well as the under-23 and under-18 side.
"I'm really pleased to be back and to be part of this exciting new structure," said Baines.
"While our development pathway is already highly respected, it has been very clear to me that there is a shared ambition here to develop and improve this even further, and I'm hugely excited to have the opportunity to play a part in this."
Director of football Marcel Brands added: "Adding Leighton and his knowledge into that structure will be very valuable to us.
"He is taking up a new and important role which he has helped design based on his recent perspective and tremendous experience as a player."
Baines joined Everton from Wigan Athletic in the summer of 2007 and went on to make 420 appearances in total for the club, scoring 39 goals.
Baines won 30 caps for the England national team and was part of their squads at the 2012 European Championship and 2014 FIFA World Cup.
