Born in Berango, Biscay, Basque Country, Astralaga started his career with the Karabigane local club. In 2014, he then moved to Athletic Bilbao's youth academy. In the summer of 2018 Astralaga came to La Masia and joined the U16 team. There he continued to grow and, through the team's youth system, he played his first match for Barça Atlètic against Betis Deportivo on 27 March 2022.
On 28 January 2023[7] Astralaga was for the first time included in the match day squad against Girona FC. In April 2023 he reached an agreement with FC Barcelona to extend his contract until June 2025. In the final game of 2023, on 22 December in Dallas, he made his unofficial senior team debut during a friendly against Club America.
International career
Ander Astralaga has represented Spain at international youth level. On 10 October 2021 he made his debut for Spain U18 against Romania U18. He played a total of six games, before being promoted to the U19 team. On 29 August 2022 Astralaga made his debut for the U19 team against Israel U19 in a friendly, which ended in a 0-0 draw. In his third match for the U19 team on 10 July 2023[8] he played against Norway U19 in the U19 European Championship, which ended in a 0-0 draw.