[1] Born and raised in Stockholm, Mendes started to play football as a youngster for local club AFC United, before moving to AIK at age 12.

[8] On 19 July 2021, Mendes was promoted to their parent club Hammarby IF in Allsvenskan, the domestic first tier, signing a two-year deal.

[9] He made his competitive debut only days later, on 22 July, coming on as a substitute in a 3–1 home win against Maribor in the UEFA Europa Conference League.

[14] On 2 September 2024, Mendes joined Swiss club Basel on a season-long loan with an option to buy.

[15][16] In 2018, Mendes won two caps for the Swedish U17 national team, playing in two friendlies against Belgium and Czech Republic.