Pjanić's second season at Juventus began with a 2–3 loss against Lazio in the 2017 Supercoppa Italiana. He scored his first goal of the season in city derby against Torino on 23 September 2017. Juventus won the game 4–0. On 28 February, Pjanić scored a crucial penalty against Atalanta to send Juventus through to the 2018 Coppa Italia Final. Juventus won that final, with Pjanić contributing by assisting for one of the goals in a convincing triumph over Milan on 9 May 2018. Four days later, Pjanić once again became Serie A champion in a game against his old club Roma, which sealed his second domestic double in two seasons. On 19 May, the final match of the season, he scored his fifth league goal of the season, netting a trademark free kick, which sealed Juventus's 2–1 home win over Hellas Verona.