Nepal—one of the most rapidly urbanizing countries in the world—has witnessed unplanned urbanization in recent decades. Nevertheless, spatial-temporal dynamics of land use land cover (LULC) in major cities of Nepal are not well understood. This study investigates LULC changes in the 12 rapidly urbanizing cities of Nepal from 1990 to 2020. Freely accessible Landsat images and Google Earth Engine (GEE), a cloud-based analysis platform were used to classify the city landscape into five major classes: vegetation, agriculture, barren, water body, and built-up using a random forest algorithm. Built-up areas have continuously increased in the Nepali cities mostly at expense of agricultural lands thus agriculture areas have decreased, and vegetation areas have followed mixed trends during each of the three decades. Biratnagar, Janakpur, Kathmandu, Nepalgunj, and Rajbiraj showed an overall increase in built-up areas at the expense of vegetation and agricultural lands while Bharatpur, Bire- ndranagar, Dhangadhi, Ghorahi, Hetauda, Pokhara, and Tulsipur showed an overall decrease in agricultural areas with increased built-up areas and vegetation from 1990 to 2020. This study will assist the policymakers, city planners, and local governments to formulate sustainable urban development strategies and plans to prevent haphazard urban growth while preserving the city’s agricultural lands to promote local food supply and green areas to ensure an uninhibited flow of ecosystem services in the cities.