Oyono was born near Ebolowa in the South Province of Cameroon. After obtaining his secondary education in Yaoundé, Oyono studied in Paris. Following Cameroon's independence, Oyono was a member of the Cameroonian delegation to the United Nations in 1960, when the country was admitted to the UN. Oyono subsequently served as Cameroon's ambassador to various countries from 1965 to 1974. He was briefly the Ambassador to Liberia in 1965, then served as ambassador to the Benelux countries and the European Communities from 1965 to 1968 and as ambassador to France, with additional accreditation for Spain, Italy, Morocco, Algeria, and Tunisia, from 1969 to 1974. From 1974 to 1982 he was Cameroon's Permanent Representative to the United Nations; he acted as President of the United Nations Security Council in place of the United Kingdom's Ivor Richard at the 1,866th meeting of the Security Council on 16 December 1975, and was Chairman of UNICEF from 1977 to 1978. From 1982 to 1985 he again served as ambassador to various countries: first as ambassador to Algeria and Libya, then as ambassador to the United Kingdom and the Scandinavian countries.