Vulnerability assessment using composite indices provides critical information for the policymakers on why certain regions are impacted more than the others. Several researchers have assessed the vulnerability to hazard in diverse spatial and environmental settings, however, not many studies have assessed the vulnerability to flood hazards in Bihar, where flooding is a perennial event. The objective of this paper is to assess the vulnerability of the flood affected districts by integrating various indicators for exposure, sensitivity and adaptive capacity into a composite index using principal component analysis. This study normalizes and aggregates across the sub-indices and combines this information with Geographic Information Systems to illustrate the social vulnerability to floods. The vulnerability index estimated in this study indicates that: 1) Bihar is highly vulnerable to floods, with north Bihar especially being more vulnerable due to recurrent flooding; and 2) there is a strong spatial pattern among the vulnerable districts. The comparison across the districts reflects that strong biophysical as well as social factors dominate and determine the varying degrees of vulnerability among the districts of Bihar. The study highlights the need to address the disaster prevention, risk reduction, and mitigation measures, as well as the endpoints to enhance the capability of adaptation to floods by the affected community.