In island areas without a water supply pipe, water use is limited to small reservoirs or groundwater. These small reservoirs depend on precipitation and are not always available due to changes in precipitation patterns. Island areas in Korea are susceptible to drought, and water supply restrictions and the transport of water from the mainland are necessary to relieve the impact of drought conditions. A method for assessing water use vulnerability that considers the unique characteristics of these islands is required to respond to water scarcity during times of drought. In developing a vulnerability assessment, we used the pressure-state-response (PSR) framework to establish indicators corresponding to pressure, state, and response. We employed objectively weighted decision-making using the entropy method to identify the indicators for each factor. To establish the weight reflecting the importance of each factor, we used subjective weighting according to the Delphi method. The water use vulnerability assessment method was developed by adding factors representing the groundwater and sea levels according to the characteristics of the islands. The results of this assessment of the water use vulnerability in island areas revealed the most vulnerable area and the water supply priority area. The method developed in this study reflects subjective opinions for water use in island areas and can be used to assess water use vulnerability by calculating the weights of specific indicators based on the differences of the alternatives. This method forms the basis for an approach to determining priority areas for transported water supply.