The Mono River in the Yoto district, presents a challenge in terms of repeated flood hazard. The eight selected communities lie in majority in the floodplains of the Mono River and experience year after year flood disaster. This study focuses on flood vulnerability assessment of the downstream part in the Mono River basin in the Yoto district. It analyses the trend in rainfall and river discharge series (1971-2010); it assesses the determinants of flood vulnerability; and it equally computes Flood Vulnerability Index (FVI). The result reveals a clear evidence of change in precipitation and river discharge patterns during the period of record. It shows an extreme variability in terms of flood magnitude and frequency in the Mono River. Besides, the closeness of households’ farmlands to the river body, the type of construction and the position of settlements, the household size, the low level education of household head, the lack of diversification of livelihood strategies, the lack of adequate flood warning system and lack of willingness and ability to take responsive actions coupled with inadequate emergency services, are identified as main determinants increasing communities’ vulnerability to flood disaster. Furthermore, FVI offers easy comparison of communities’ vulnerability to flood disaster.