Houaiss began his career in Rio de Janeiro as a professor of the Portuguese language, of which he eventually became a recognized authority. He left teaching in 1945 for the diplomatic service and served the Brazilian government as such until the 1964 military coup, when he was forced to retire with loss of political rights. During that period he was Brazilian vice-consul and representative to the United Nations in Geneva, Switzerland (1947 to 1949); third secretary of the Brazilian Embassy in the Dominican Republic (1949 to 1951) and in Athens, Greece (1951 to 1953); member of the permanent Brazilian delegation to the United Nations in New York City (1960 to 1964).