The 24-year-old Cameroon international will now travel to the Nou Camp to agree personal terms and undergo a medical, Arsenal announced in a statement on their website.
Barcelona confirmed in a statement the fee for Song will be 19million euros (?15million).
The Barcelona statement read: "Barcelona have agreed a deal with Arsenal for the transfer of Alex Song to the Nou Camp. The fee is 19 million euros
"The Cameroon international midfielder will sign for the next five seasons with a release clause of 80 million euros.
"On Monday he'll have a medical and then join the rest of the squad for the official team presentation at the Joan Gamper Trophy."
Barca, who begin their Primera Division campaign against Real Sociedad on Sunday, face Sampdoria in the Joan Gamper Trophy on Monday evening at the Nou Camp.
Source: PA
Source: PA