The details are outlined by Diario Sport, who say that the Catalan giants fought off competition from Liverpool and Atletico Madrid to secure the signing.
The Catalan giants have paid an additional €3.5m deal to complete the transfer after holding a €1m deposit on a player who has yet to play a senior match for the Brazilian club.
Maia is known as a pacey forward with strong finishing ability and an eye for a pass but it is no doubt unusual that he is yet to play a professional game in his home nation before securing a switch to European football.
Barcelona transfer news has been dominated by their pursuit of Inter striker Lautaro Martinez and the arrival of Miralem Pjanic from Juventus, with the club extremely busy in restructuring their squad.
However, it is unlikely that Maia will be involved in the first-team squad at all at the Blaugrana next season and he will instead play with their B side in Segunda B, after they failed to secure promotion to the second tier.
Maia has impressed for the club’s underage sides, as well as the Brazilian Under-16 and Under-17 sides.
He joined Sao Paulo as a 14-year-old and he scored 30 goals in 36 appearances during the 2018 calendar year and hit 21 the following year.