On 12 August 2018, Dembélé scored the winning goal against Sevilla in the Spanish Super Cup, in an eventual 2–1 victory to win Barcelona their 13th Supercopa de España title. He opened his La Liga season's goal tally by scoring the only goal of the game against Real Valladolid, on 25 August, away at the José Zorrilla. A week later, on 2 September, Dembélé notched his first home goal of the season, as the "Blaugrana" demolished newly promoted Huesca 8–2. Dembélé was again on the scoresheet the very next game, on 15 September, netting his third match winner of the ongoing campaign in a 2–1 away victory over Real Sociedad at the Anoeta. On 18 September, Dembélé scored his first Champions League goal of the season, helping "Barça" defeat PSV Eindhoven 4–0 at the Camp Nou. Coming on as a substitute against Real Madrid, on 28 October, Dembélé set up Arturo Vidal's last goal of the game in a 5–1 home El Clásico triumph. Just a week later, again appearing from a bench role, he inspired Barcelona to a 3–2 comeback away against Rayo Vallecano, scoring the 2–2 equalizer with a half-volley in the 87th minute.