In 1953, Serrano joined the Chilean diplomatic corps and was stationed in India until 1963, where he took a keen interest in Hinduism and wrote several books. He was later made ambassador to Yugoslavia and then Austria, and while in Europe made contacts with various former Nazis and other far-rightists living on the continent. Following Chile's election of a Marxist President, Salvador Allende, Serrano was dismissed from the diplomatic service in 1970. After Allende was ousted in a coup and Augusto Pinochet took power, Serrano returned to Chile in 1973. He became a prominent organiser in the Chilean neo-Nazi movement, holding annual celebrations of Hitler's birthday, organising a neo-Nazi rally in Santiago, and producing a neo-Nazi political manifesto. He wrote a trilogy of books on Hitler in which he outlined his view of the Nazi leader as an avatar. He remained in contact with neo-Nazis elsewhere in the world and gave interviews to various foreign far-right publications.