The study aims to compare land use land cover (LULC) change between Bangladesh and Indian Sundarbans from 1975 to 2020 using Landsat Satellite images. We performed supervised maximum likelihood (ML) to classify the study area at four time periods over 45 years (1975, 1990, 2005, and 2020). The classification was assigned to five classes: dense forest, moderate forest, sparse forest, barren land, and water body. Accuracy assessment of the classified images was completed with 250 control points for each year. The findings of our study revealed that the dense forest cover of Bangladesh and Indian parts was 54% and 31%, respectively, whereas, for the whole Sundarbans, it was 45% in 1975. However, the dense forest of Bangladesh and Indian Sundarbans decreased by an annual rate of 1.20% and 1.60%, respectively, from 1975 to 2020. From 1990 to 2005, Bangladesh Sundarbans slightly increased the dense forest cover by an annual rate of 0.68%, while the Indian Sundarbans decreased by an annual rate of 0.63%. The moderate dense forest of Bangladesh and Indian Sundarbans increased by giving almost the same annual rate of 3.62% and 3.59% from 1975 to 2020, whereas the increasing rate of the sparse forest was much higher for Bangladesh (8.36%) Sundarbans than Indian (3.36%) parts. The water bodies of Bangladesh and Indian Sundarbans increased by giving an annual rate of 0.48% and 0.71%, respectively, from 1975 to 2020. Our study found that most of the barren lands were located near the boundary between forest and human settlement of Indian Sundarbans compared to Bangladesh. The findings of the comparative assessment between these two countries can support sustainable forest management and planning by considering the best policy options.