He won the Academy Award for Best Costume Design, which he shared with Yvonne Blake for their work on Franklin J. Schaffner's epic period drama film Nicholas and Alexandra (1971).
He was educated in his home city at the Colegio del Pilar and the University of Madrid before studying in Granada at the El Sacro Monte.
Castillo, together with Pierre Balmain, Cristóbal Balenciaga, and Christian Dior, were the new generation of Paris designers after World War 2.
From 1950 to 1962, the salon was known for elegant clothes, slender lines, long flowing skirts in rich fabrics, and elaborate embroideries.
[3] His assistant at Lanvin for ten years until 1962 was Dominic Toubeix who went to New York and became a Coty Award winning designer there,[4] before returning to Paris in 1974 to present a couture collection in Castillo's name.