Tiago Coser was born in Chapecó, Santa Catarina, on 16 January 2004 and was formed at Chapecoense, joining the club's under-17 side in 2019 and being registered with the senior squad from February 2021. He also holds Italian citizenship.

Benfica signed him in January 2022 and he was immediately attached to the B team, filed in Portuguese records under the single name Tiago. A central defender of 1.91 m, he wore the numbers 92, 73 and 43 at various points and combined under-19 and under-23 football with a limited role in the reserve side, making four appearances in the Liga Portugal 2 in 2022/23. He did not play for the first team.

Coser returned to Brazil in February 2025, signing for Coritiba on a contract to 2027.