A lawyer by profession, Benito Castejón became involved in sport as a professional field hockey player, representing the Spanish national team. Following his playing career Castejón moved up into sports administration and was appointed as the National Secretary of the Delegation for Physical Education and Sports in 1967. A decade later he became the National Delegate for Physical Education and Sports. In 1977 the Higher Council for Sports (CSD) was created by the Spanish government with Castejón serving as its first Director General. One year earlier he was elected as the President of the Olympic Committee of Spain, remaining in that role until 1980, with him being awarded with the Olympic Order in Silver in the same year.