On 31 January 2020, Barcelona announced that they had reached agreement with Palmeiras for the transfer of Fernandes, who would join the Catalan club ahead of the 2020–21 season at the end of September, after completing his loan spell with Real Valladolid. "Barça" paid a fee of €7 million plus €3 million on add-ons, and the player agreed to a five-year contract with the club. On 24 November, he made his first and only appearance for Barcelona's first team and also in the UEFA Champions League when he replaced Pedri for the final 17 minutes during a 4–0 away victory against Dynamo Kyiv in a Champions League group stage match.