The 29-year-old Elano will be returning to the Brazilian club after five years in European football with Shakhtar Donetsk, Manchester City and Galatasaray.
The playmaker was a starter for Brazil in the 2010 World Cup until hurting his ankle against Ivory Coast in the group stage.
Elano has been officially introduced to fans on Sunday before the team's final Brazilian league match, against Flamengo.
Santos is seventh in the 20-team standings but it has already secured a spot in next year's Copa Libertadores because it won the Brazilian Cup.
Elano will be joining young sensation Neymar.
The Brazilian team will pay about 2.9 million euros to Galatasaray as transfer fee and if Elano changes clubs before Dec. 31, 2012, half of the profits from the sale will be given to the Turkish side.