On 16 April 2018, Peña renewed his contract with Barça for three seasons, with an option for a further two.[5] He was later promoted to the reserves in Segunda División B ahead of the 2018–19 season,[6] and made his senior debut on 6 October 2018 by starting in a 1–1 home draw against CD Atlético Baleares.[7]
Peña once again featured on the bench for the main squad during the 2019–20 campaign, to cover for Neto's absence due to injury.[12] On 6 October 2020, Barcelona exercised the option on Peña's contract to extend it for a further two years.[13]
Loan to Galatasaray
On 31 January 2022, Peña joined Galatasaray on loan for the remainder of the season.[14] He made his professional debut in the Süper Lig on 6 February in a 1–1 draw at Alanyaspor under former Barcelona assistant Domènec Torrent,[15] He had a record of two draws and as many wins before club icon Fernando Muslera began his return from injury;[16] by the second half of March, after elimination from the UEFA Europa League by Barcelona, the Uruguayan won his place back.[17]
Return to Barcelona
Peña returned to Barcelona as his loan deal expired, and made his official first team debut under manager Xavi in a 4–2 away win over Viktoria Plzeň in the UEFA Champions League on 1 November 2022.[18]
On 3 January 2023, Peña was registered as a first team player, and was handed the number 13 shirt left vacant by Neto, who had left for AFC Bournemouth.[19]
On 9 May 2023, Peña signed a contract extension with Barcelona, keeping him at the club until 2026. The new contract included a buyout clause of 400 million euros.[20]
Near the end of the season, Peña played against Real Valladolid and Celta Vigo, where he played a total of approximately 72 minutes of match time, after coming on for Marc-André ter Stegen at Valladolid at half time, and coming on at Celta at 63 minutes. He conceded 2 goals in 2 appearances.
During a match against Villarreal on 22 September 2024, ter Stegen suffered a patellar tendon injury, which would force him to miss the rest of the season. Peña immediately replaced him in the 45 minutes of the first half, which ended in a 1–5 away victory.
Due to the isolation of some national team players following the positive COVID-19 test of Sergio Busquets, Spain's under-21 squad were called up for the international friendly against Lithuania on 8 June 2021. However, Peña did not play.[23]