The Cameroon international makes official his 19 million euro move to Camp Nou, penning a five-year contract to provide competition for the likes of Sergio Busquets.
The 24-year-old Cameroon international was left out of the Gunners' squad for the team's opening Premier League fixture against Sunderland after which the north London club confirmed that it had agreed terms on the deal with the Spanish champion.
Song, who joined Arsenal back in 2005 from French side Bastia, has penned a five-year deal and will provide competition for Sergio Busquets at the base of Barcelona's midfield.
"Everyone at Arsenal would like to thank Alex for his contribution to the club and wish him the best of luck for the future," read a statement on the Premier League side's website.
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