Islam joined the Kushtia College as a lecturer in Biology and then served in the Biology and Botany departments of the University of Dhaka as lecturer (1952-1962), reader (1962-1972), professor (1972-1990), supernumerary professor (1991-2000) and honorary professor (2001-2006) [REF].
Islam served as the president of Asiatic Society of Bangladesh during 1992-94 and Bangladesh Botanical Society during 1985-1986 [REF].