On 1 July 2020, Mármol renewed his contract with Barça and was definitely promoted to the B-team.[5] He became a regular starter for the side, and scored his first senior goal on 17 January 2021, in a 3–1 away loss against Gimnàstic de Tarragona.
Mármol made his first team – and La Liga – debut for Barcelona on 15 May 2022, replacing fellow youth graduate Alejandro Balde late into a 0–0 away draw with Getafe CF.[6][7]
Andorra
On 30 August 2022, Mármol signed a two-year contract with Segunda División newcomers FC Andorra.[8] He became a regular starter for the club, and scored his first professional goal on 27 May 2023, netting his team's second in a 4–3 home win over Villarreal CF B.