Arthur made his competitive debut at the 2018 Supercopa de España on 12 August, in which Barcelona won 2–1 over Sevilla. Arthur made his league debut during the first league match of the season, also registering his first assist for the club in a 3–0 win against Alavés. On 31 August 2019, Arthur scored his first goal for Barcelona in 2–2 away draw against Osasuna.