Prior to his appointment as Minister of Health, he served in the Maldives Permanent Mission to the United Nations in New York from September 1976 until early 1978 as Councellor, Minister Councellor, Deputy Permanent Representative and Deputy Head of the Department of Foreign Affairs of Maldives and finally as the Permanent Representative. When he served as the Permanent Representative of Maldives to the United Nations he was concurrently accredited to India and Pakistan as Non-Resident Ambassador.
Mr. Hussain graduated form the Armidale College of Advanced Education, New South Wales, Australia, with a Diploma in teaching in 1973.
Until July 1974 he taught at the Majeediyya School in Male, Maldives. He was then appointed as the Director of Radio Maldives where he served till his transfer to the Ministry of Education as Under Secretary in July 1975.
In early 1976 Mr. Hussain was transferred to the Department of Home Affairs as Under Secretary responsible for Atolls Division. Later that year he was transferred to the Department of External Affairs as Under Secretary to take charge of Foreign Investment Division, where he served until his appointment to the Maldives Permanent Mission to the United Nations.
Mr. Musthafa Hussain represented Maldives at numerous meetings of International Organizations, namely: the Food and Agricultural Organization; the Colombo Plan; Organization of the Islamic Conference; World Health Organization; the South East Asia Regional Committee of WHO; the Commonwealth Health Ministers Meeting; Served on the WHO Executive Board.
He has served as the Chairman of the Regional Committee of WHO South East Asia Region, Vice President of the World Health Assembly and Chairman of the WHO Executive Board.