Anthropogenic activities within and around the protected areas are one of the major reasons for damaging forest cover and threat to the sustainable management of the forest. In Bangladesh, many protected areas are facing constant anthropogenic threats to their biodiversity and forest cover. Fasiakhali Wildlife Sanctuary (FWS) is one of the few protected areas in Bangladesh, the last resort for a few herds of Asian elephants (Elephas maximus). The presence of Asian elephants is under constant threat as the forest cover is changing rapidly, leading to exposure to elephant-human conflict. However, there is not enough scientific analysis on forest cover change of Fasiakhali Wildlife Sanctuary. This study was conducted to understand the forest cover change dynamics from 1990-2020 using Landsat 5 TM and Landsat 8 OLI/TIRS images. Landsat 5 TM of 1990 and 2005 and Landsat 8 OLI of 2020 had been used to determine the forest cover change. A supervised classification technique was used for forest cover mapping using a maximum likelihood classification algorithm. The study showed that about 6.8% and 8.6% of forest cover were transformed into non-forest use (e.g., agricultural land and bare land) between 1990-2005 and 2005-2020. Most of the conversion has happened to agricultural land, which was about 200 ha from 1990 to 2020. Primarily, it was found that illegal tree cutting and transforming forest land to the agricultural field were the anthropogenic reasons behind forest cover change. This study could be the essence for a better understanding of habitat fragmentation and monitoring illegal activities inside the Fasiakhali Wildlife Sanctuary for prospects.