Fla vice-president Marcos Braz has confirmed that Mari has been sold to Arsenal for a fee believed to be in the region of £14million, reports The Sun.
Since joining from the Brazilian club in January, the 26-year-old has featured in just three games in all competitions, as he arrived at the club lacking match fitness.
And his season has already been cut short after he suffered an ankle injury in the 3-0 defeat against Manchester City last week, leaving him out of action for up to five months.
Mikel Arteta revealed after the loss to City that Mari's signing remains a priority, despite his ankle knock.
Asked whether the club will still press ahead with a move, he said: "Yes.
"This cannot be affected just because a player gets injured doing his job and defending our club."