 In his first match upon his return to the "Estadio Benito Villamarín", on 15 January 2018, he replaced Sergio León late into the home fixture against CD Leganés and scored the 3–2 winner through a penalty.On 13 July 2018, after cutting ties with Betis, 37-year-old Castro returned to his first club Las Palmas on a two-year contract..

Castro's two older brothers – Rubén was the youngest of five siblings – Guillermo and Alejandro, were also footballers.At one point in their careers, they also represented hometown's Las Palmas.