The 32-year-old Argentine striker was long expected to join Barcelona after a decade with Manchester City.
Barcelona confirmed that an agreement had been reached for Aguero to join the club on July 1, once his current City contract expires.
He signs until the end of the 2022-23 season, with a buyout clause of 100 million euros.
Aguero was unveiled to the Spanish media on Monday at the Camp Nou, where he spoke about his desire to play alongside close friend and compatriot Lionel Messi who is yet to sign a contract extension with the Catalans.
“Let’s hope we play together… what happens with Leo is down to decisions that he will make with the club,” Aguero told reporters.
“Obviously it will be a pleasure if we play together. If he continues here, which I think he will, we will try to do our best for the club as he always has done.”
Aguero’s signature comes 12 months after Barca let Luis Suarez depart, joining Atletico Madrid whom he led to the 2020-21 La Liga title.
Barca have also been in the market to sign Borussia Dortmund’s Erling Haaland, joining the race alongside Real Madrid, Chelsea and Manchester City.
Aguero scored 260 goals for City across a decade, including a dramatic final day winner as they won their breakthrough 2011-12 Premier League crown.