In September 1971 Luns was nominated as the next Secretary General of NATO, he resigned as a Member of the House of Representatives the same day he was installed as Secretary General, serving from 1 October 1971 until 25 June 1984. Luns retired after spending 31 years in national politics and became active in the public sector served as an diplomat and lobbyist for several economic delegations on behalf of the government and as an advocate for United States–European Union relations and European integration.