The Arun River, a transboundary perennial river flows from China to Nepal along with the Arun tectonic window, East Nepal. The Arun River watershed experiences significant slope instability as landslides occur frequently every year. The present study aims to prepare a landslide susceptibility map of the northern stretch of the Arun River watershed. The study area lies on the northern stretch of the Arun River watershed where both lesser Himalayan and higher Himalayan rock units are located. The GIS-based Weight of Evidence method is adopted in this research to identify the landslide susceptibility. Field investigation of the study area concludes that the combination of the following five parameters including topography, hydrology, geology, land use pattern, and intense rainfall with seasonal snowfall, play a crucial role in the landslide events in this region. A landslide susceptibility map is developed incorporating the consideration of the slope characteristics (slope angle, slope aspect, and slope shape), as well as the stream proximity, the stream power index, the lithology, and the land-use practices. The results show that 83% of the past landslides lie within the high to very high susceptibility zone in the map. The present study demonstrates that the development of the landslide susceptibility map could have a significant impact on the landslide hazard risk mitigation and land use management in this region.