Abstract. Mamnun M, Hossen S. 2021. Spatial alteration of fragmented landscape in evergreen and semi-evergreen rainforest: A case study in Chittagong Hill Tracts, Bangladesh. Asian J For 5: 17-27. The principal aim of the study was to explore the level of fragmentation and underlying drivers in forests of Bandarban Sadar Upazila, Chittagong Division, Bangladesh from 1988-2018. The ArcGIS v10.5 and ERDAS Imagine v15 software were used to process satellite imageries and assess quantitative data. The study revealed that the area under forest land decreased very rapidly; it was lost about 7165.13 ha and the annual destruction rate was 17.92%. The edge density of forest area and agricultural crops rapidly increased from 1988-2018, while barren land and water bodies were almost consistent. Forest land became fragmented as its total edge area increased by 275.87% from 16469.6 km in 1988 to 61905 km in 2018. There was gradual decline in Shannon Diversity Index from 1988 (1.004), 2003 (0.878), and 2018 (0.615). Among the different factors, agro-horticultural plantation was the main factor for reduction in landscape diversity. This analytic study would help policymakers take necessary steps for sustainable forest management.