The 29-year-old will rejoin the club he left in 2008, having been released by AC Milan earlier this summer, after putting pen to paper on a contract worth £50,000-a-week
Mathieu Flamini has become an Arsenal player for the second time after signing a two-year contract with the Gunners.
The Frenchman put pen to paper on the deal after reaching an agreement with the club following a final round of talks on Wednesday.
Goal understands Flamini will be paid £50,000-a-week and that the contract includes an option for a third year.
Arsenal will announce the deal after receiving the final clearance from the Premier League.
Flamini will be the second signing of the summer for Arsene Wenger — both free transfers — and the fourth old boy the manager has re-signed in recent years, following Sol Campbell, Jens Lehmann and Thierry Henry.
Arsenal anticipate the deal will herald an intensive recruitment drive in the last five days of the window.
Wenger's top target is Angel Di Maria and he has not given up hope of signing Wayne Rooney, Yohan Cabaye or a new goalkeeper.
Flamini was released by AC Milan at the end of last season and he has been training with the Gunners for the last three weeks while working on his fitness and looking for a new club.
Wenger decided to make the 29-year-old an offer after being impressed by his condition and attitude.
The France international, who quit Arsenal for Italy in 2008, will strengthen the central midfield and also offers the versatility of being able to fill in at full-back.
Flamini becomes the second Frenchman to join Arsenal this summer on a free transfer following Yaya Sanago, who signed after being released by Auxerre.