The 32-year-old was in Spain on Monday to sign a pre-contract agreement with the La Liga giants once his contract at City expires at the end of June.
Aguero’s departure from the Etihad was announced in March, with City deciding not to hand the Argentine a new deal after ten years at the club.
The club’s decision was met with confusion and skepticism given Aguero’s service and 260 goals for the club.
A host of clubs were immediately linked with Aguero and goal-shy Chelsea headed the list from the Premier League, with Thomas Tuchel expressing an interest in the former Atletico Madrid man.
However, Aguero insists ‘best team in the world’ Barcelona were the only option for him and he had no intention of staying in the Premier League.
‘I didn’t even hesitate. I didn’t want someone else to talk to me, just Barca,’ said Aguero.
‘(Pep) Guardiola, when we won the Premier League, he told me ‘You’re going to the best team in the world’.
‘As a boy I said one day they will surely notice me and here I am.’
Aguero ends his City career as the club’s top scorer and most decorated player but his time in the north-west ended in disappointment on his final game as Chelsea beat Guardiola’s side 1-0 in the Champions League final.
The Argentina international was a late substitute in Porto but failed to make an impact as a below-par City were well beaten.