Cameroon midfielder Alex Song signed a five-year contract with Barcelona on Monday, bringing an end to his time with Premier League club Arsenal.
Song posed for the traditional photo in front of the club's insignia before passing a medical examination and meeting with Barcelona President Sandro Rosell.
"I'm very happy to be here because everyone knows that this is the best team in the world,'' said Song.
"I always wanted to play for Barca, with Cesc Fabregas, (Lionel) Messi and (Andres) Iniesta. It is a great day for me."
Song was brought in to replace Seydou Keita, who played a limited, but important role in providing Barcelona with a more physical presence in midfield.
"I always wanted to play for Barca, with Cesc Fabregas, (Lionel) Messi and (Andres) Iniesta. It is a great day for me"
"I want to fight for a place on the team,'' Song said.
The Spanish club paid Arsenal $23.4 million for Song.
Arsenal sold striker Robin van Persie to Manchester United earlier this week for $38 million.
Barcelona coach Tito Vilanova said he was impressed with Song's versatility.
"(Song) can provide us with a lot of things. He's very good, he recovers the ball well and then can do good things with it," said Vilanova, who sees Song sharing time with Sergio Busquets as a defensive midfielder alongside the more attack-minded Iniesta and Xavi Hernandez.
"Busquets can't play every game of the season so Song will be a great addition,'' he said.
"And he can also play in the center of the defence. With him we'll have more alternatives (because) he can play in three different positions.''
Song is Barcelona's second signing this summer after defender Jordi Alba, who joined from Valencia.
Barcelona thrashed Real Sociedad 5-1 in their Spanish league opener on Sunday.
On Thursday, Barcelona host Real Madrid in the first leg of the Spanish Supercup.