He still has 12 months left to run on his contract with Barca, but no longer figures in their future plans.
Sporting have been linked with his services for some time and the France international will now link up with them on a trial basis.
A statement released by Barca on the club’s official website read: “FC Barcelona has granted permission for defender Jeremy Mathieu to train on a trial basis during his holidays with Sporting Club de Portugal.
“Once this period is over, the two clubs and the Frenchman will make a decision on the player’s future.”
Any potential deal for Mathieu has been delayed as he was among those in attendance at Lionel Messi’s wedding on Friday.
He will be leaving Barca after three years, in which time he has made 91 appearances and scored four goals.
Just 16 of those outings came in the 2016-17 campaign, with the Frenchman slipping out of favour.