In the following season, Cancelo became a starter earning his debut in the UEFA Champions League on 16 September, where he scored his first goal for Los Che in a 2–3 home loss to Zenit Saint Petersburg. In doing so, he became the fifth youngest scorer in the history of Valencia in the Champions League (aged 21 years and 107 days). On 2 December, Cancelo scored his first goal Copa del Rey in a 3–1 victory over Barakaldo. Valencia was eliminated from the tournament after losing 8–1 on aggregate to Barcelona. He also netted for the first time in the league the following 20 April to conclude a 4–0 win over Eibar at the Mestalla Stadium.
