Within a changing world where freshwater resources are coming under increasing pressure, assessing water system vulnerability is critical for enabling adequate water resource management. Quantitative assessments of socio-economic and environmental factors which contribute to water system vulnerability can provide a strong evidence base on which to base decision-making. A range of drivers including population growth, agricultural intensification and industrial activity are placing greater demand on freshwater supplies in Western Australia. In combination with changing climatic conditions resulting in a warmer and drier environment in southwest Western Australia, these pressures have diminished the quantity of available freshwater supplies for agricultural districts. In this paper we provide a quantitative assessment of water supply and demand vulnerabilities for the Wheatbelt region of the state of Western Australia (WA). This region provides significant agricultural and mineral resource contributions to the state economy. The potable water supply for human consumption in this region is almost entirely drawn from a different geographic area, and conveyed by means of an extensive pipeline network to the Wheatbelt region. Competition for freshwater resources is high with increasing population pressures from expansion of the state's capital city, Perth, encroaching north- and eastwards into the Wheatbelt. To assess water vulnerability we conceptualise the water system components and select a series of socio-economic and environmental indicators which best represent the inherent vulnerabilities associated with water supply and demand in the Wheatbelt. Water supply, demand and overall system vulnerabilities were spatially assessed for the years 2001, 2006 and 2011. Results indicate that biophysical indicators of supply capacity have the greatest influence on overall vulnerability for each time period, however the spatial variability of specific vulnerability factors is much more nuanced. Our assessment of water vulnerability will enable water resources managers and policy-makers within the Wheatbelt and at the state level to better assess water supply and demand pressures. However, our robust methodology also allows for transferability to other locations experiencing water stress as a comprehensive approach for examining historic and future impacts of water resource availability on socio-ecological systems.