The aim of the present study is to investigate the risk of climate change on Istanbul. Istanbul is the largest city, in terms of both population and economic activity capacity, in Turkey meaning that any climate-related risk would be destructive not only for the city but also for the country. The urban system has been identified based on urban sectors that are the issues of activities, management areas, ecological systems, resources and species and critical for economic viability and public health of the city, also likely to be affected by climate-related disasters. 11 urban sectors and 25 sub-sectors, which are also presented as planning areas, have been determined considering the development strategies of Istanbul as water resources, health, energy, agriculture, transportation, development and land use, public safety, infrastructure, biodiversity and ecology, culture and materials. ICLEI's handbook titled "Preparing for Climate Change: A Guidebook for Local, Regional and State Governments" guided the risk assessment of these planning areas and sectors. The data has been obtained via in-depth interviews with city stakeholders and the sectors have been ranked considering the risk factors of each. The results of this study reveal the urban sectors that are under the greatest and lowest risk due to the impacts of climate change. Highlighting the climate change risk on vital sectors of Istanbul is essential for decision makers to develop further strategies to mitigate the impacts of climate change and adapt the upcoming impacts.