The Kosi River is an important tributary of the Ganges that passes through China, Nepal and India. With a basin area of 71 500 km2, the Kosi River has the largest elevation drop in the world (from 8 848 m of  Mount Jolmo Lungma(Mt.Everest) to 60 m of the Ganges plain) and covers a broad spectrum of climate, soil, vegetation and socioeconomic zones. The basin suffers from multiple water related hazards including glacierlake outburst, debris flow, landslide, flood, drought, soil erosion and sedimentation. This paper describes the characteristics of water hazards in the basin based on the literature review and site investigation covering hydrology, meteorology, geology, geomorphology and socioeconomics. Glacierlake outbursts are a huge threat to the local population in the region and   usually further trigger landslides and debris flows. Floods are usually a result of interaction between manmade hydraulic structures and the natural environment. Droughts tend to last over long periods and affect vast areas. Debris flows are widespread and occur in clusters. Rapid population increase, decline of ecosystems and climate changes have further exacerbated water related hazards in the region. Finally, the paper has proposed a set of mitigating strategies and measures.