On 21 January 2012, aged just 17, he made his first team debut by coming on as a second-half substitute in a 2–1 Campeonato Paulista home win against Oeste.
[2] He made his debut for the club on 30 September, replacing Clarence Seedorf late into a 2–0 away loss against Bahia for the Série A championship.
[citation needed] Bruno Mendes scored his first goal for Bota on 14 October 2012, netting the equalizer in a 1–1 away draw against Grêmio.
Five days later he scored a brace in a 3–2 home win against Vasco da Gama, and finished the month with five goals in six matches.
[citation needed] In November 2012, former Guarani player Andrei Frascarelli claimed the club owed him wages and asked the court to grant the rights of Bruno Mendes to him.