The Rio Santa valley in the Cordillera Blanca, Peru, has been repeatedly affected by severe glacial flood disasters in the past decades. The continuing high rate of glacier retreat has led to the formation and rapid growth of a large number of glacial lakes. Due to the risk of lake outburst floods, downstream communities are confronted with serious hazards. The regional capital of Huaraz is one of the major sites exposed to these hazards. Mainly due to a lack of resources, no systematic evaluation of the existing hazards and related risks has been performed so far, nor have adequate warning systems been installed. Strict financial limitations make a prioritization of mitigation measures a necessity. Vulnerability assessments are an effective tool to this end. In this article, we present a method to measure the vulnerability of Huaraz to hazards from glacial lake outbursts integrating both physical (ie hazards-related) and socioeconomic factors. The difficulty of quantifying socioeconomic variables and its combination with physical factors, as well as a lack of corresponding concepts, is a challenge for measuring vulnerability. The resulting map shows a high vulnerability for several parts of Huaraz. The results of this study thus make an important contribution to effectively addressing the identified protection deficit and to efficiently assigning the limited resources in the context of a developing country. However, this article also shows the strong need for more vulnerability research integrating both physical and social science components and related theoretical frameworks to be readily applied in practice.