The 24 year old left the Latics at the end of last season after his contract expired with the club and he has been looking for a new team throughout the summer.
The Argentinian international has now joined German Bundesliga club Werder Bremen on a three year contract.
"Werder have a very good name and the Bundesliga is a very attractive league. I want to show what I am capable of here," said Di Santo of his new club.
Whilst Bremen general manager, Thomas Elchin told the club's official website: "We are very confident that we have found a good solution in Franco Di Santo.
"He is experienced but still possesses enough potential for development in order to make a great leap forwards."
As di Santo is 24 years of age the Latics are not entitled to compensation that would be available if he were under 24.
