On 10 July 2019, Díaz signed for Portuguese club FC Porto on a five-year contract, with the club buying 80% of his economic rights for a fee of €7 million. Zenit Saint Petersburg had also wanted to sign him, but he was convinced otherwise by compatriot former Porto players Radamel Falcao and James Rodríguez, as well as his then national team coach Carlos Queiroz. Díaz also admitted that prior to his Porto move, he had signed a pre-contract with Cardiff City, but the move never materialised.
