The Belarussian has been waiting for the two clubs to agree a deal after he agreed personal terms and he will now fly to the Catalan capital to undergo a medical and sign for the Blaugrana.
Arsenal recognised that they were not going to be able to hold on to the 27 year old and it was just a matter of time before he left the club this summer.
Hleb will be the first Belarussian to play for the Catalan giants and will make his debut for the club on their trip to Scotland against Hibernian on July 24.