The Modelling and Simulation Society of Australia and New Zealand Inc. All rights reserved. The management of island water systems in highly developed tourism destinations of developing countries presents many challenges in the face of climate change. Such systems are high levels of uncertainty and complexity driven by dynamic interactions amongst multiple climatic and non-climatic drivers with many feedbacks. Understanding complex interactions and feedbacks in the systems is, therefore, critical to develop a long-term strategy for safeguarding a growing water demand from socio-economic development. In this study, an integrated approach was applied to improved management of scarce water resources in Cat Ba Island under high levels of climate change and socio-economic stressors. Specifically, a range of relevant historical data was collected and examined to identify interrelations among climatic and non-climatic drivers on the island water resources. In addition, 961 households in six communes and one town in the Cat Ba Island were interviewed to understand respondents' perspectives on threats and adaptation options for the management of the island's scarce water system. Results of relevant historical data analysis and respondents' perspectives were used together with focus group discussions to develop a causal loop diagram (CLD) for the Cat Ba Island's scarce water resource system under high levels of climate change and tourism development. The CLD provides a comprehensive representation of the island's scarce water resources driven by multiple relationships and interactions amongst climatic and non-climatic drivers as well as adaptation options, represented by two reinforcing loops (R1 and R2), and ten balancing loops (B1 to B10). These loops provide further information on the potential water scarcity in the island in both current and future conditions. Specifically, water demand has been observed to be significantly increased over time due to high levels of population growth and tourism development, depicted by two reinforcing loops (R1 and R2). However, water supply has been decreasing over time due to sea level rise and precipitation decline. These observations are represented by ten balancing loops (B1 to B10) in which seven balancing loops (B4 to B10) represent a "Drifting goals" system archetype to seek the stability in water availability in the system. The next stage of this study is to apply a system dynamics model (SDM) to assess the vulnerability of the island water system in 47 years, from 2014 to 2050 under climatic and non-climatic changes. Simulations targets the year 2050 because it provides a long-term perspective from which the long-term dynamic behaviour of the island water system and the consequences of the plausible future scenarios could be assessed to inform adaptation decision-making. The key climatic and non-climatic drivers and adaptation options from the CLD will be incorporated into the SDM to assess the vulnerability of the island water system and effectiveness of adaptation options under climate change and socio-economic stressors over time. The SDM will be calibrated using relevant historical data, and validated by local stakeholders for decision-making supports. A contingent evaluation method is also applied to examine the determinant factors influencing respondents' willingness to pay (WTP) for building reservoirs and increasing water price for improved management of scarce water resources in a highly developed tourism island under climate change. The logistic regression models and Bayesian networks will be used to identify determinants of the respondents' WTP for the management of the island's scarce water system. The results of this study will assist decision-makers and water managers to understand dynamics behaviour of the system over time, and respondents' perceptions, thereby applying more effective practices to the management of scarce water resources under high levels of climate change and tourism development in the Cat Ba Island, Vietnam.