However, ownership eventually passed to Rumasa, a holding company owned by José María Ruiz Mateos.

In 1975, Banco Atlántico expanded its international presence by establishing an agency in New York, which remained operational until its closure in 2001.

In 1983, the Spanish Socialist government under Felipe González and Miguel Boyer nationalized Rumasa, including Banco Atlántico.

At the time, Rumasa was a conglomerate of 20 banks and approximately 300 other companies, and its financial troubles were too large for the Corporación Bancaria to manage.

In 1984, the Arab Banking Corporation (ABC), in partnership with BBVA and Allianz, acquired Banco Atlántico from the government.