Islam worked in the Institute of Theoretical Astronomy (later amalgamated to Institute of Astronomy, Cambridge) from 1967 until 1971. Later he worked as a researcher in California Institute of Technology and University of Washington. During 1973–1974, he served as the faculty of Applied Mathematics of King's College London. In 1978, he then joined the faculty of City University London until he returned to Chittagong in 1984. In 2006, he was made Professor Emeritus at the University of Chittagong.