Husain was repatriated from Pakistan in late 1973. Since then he worked in Ministry of Foreign Affairs in various positions. He was reportedly selected to be Bangladesh's ambassador to Cairo before the coup of August 15. He served as Foreign Secretary, of Government of Bangladesh from 15 November 1975 to 6 September 1978. During the period, he visited summit level meetings in nine countries on bilateral visits. He also visited Moscow twice in November 1975 and 1976 as a single member delegation to discuss bilateral issues. For the period of 1978–1982, He was ambassador of Bangladesh to United States of America. In his tenure, President Ziaur Rahman visited in United States in 1980.
