Born in Barreiras, Bahia, Iago Mendonça represented Atlético Goianiense, Jardim América and Trindade as a youth.
He made his senior debut with the latter on 11 June 2017, playing the last six minutes of a 1–0 Campeonato Goiano Segunda Divisão away win against ASEEV.
[2] He made his first team debut for the Esmeraldino on 20 March 2019, starting in a 2–1 home win against Iporá for the Goiano championship.
[4] On 22 August 2020, after being rarely used, Iago Mendonça was loaned to Série D side Aparecidense for the remainder of the season.
[5] He returned in October after failing to make an appearance, but still made his Série A debut on 3 December by starting in a 0–3 home loss against São Paulo.