Water authorities in West Java, Indonesia have difficulties in implementing water improvement programs due to lack of tools for prioritisation of water-related issues and their respective programs. To facilitate more efficient management of the water resources, the West Java Water Sustainability Index (WJWSI) was recently developed. This paper outlines the tasks for developing WJWSI and highlights the results of its application in one of West Java catchments, Citarum catchment. The results showed that five out of the thirteen indicators and sub-indicators, namely ‘Water Availability, Water Quality, Education, Water Loss and Poverty’, had low sub-indices and thus had poor performances. Then, the sub-indices were aggregated using the geometric aggregation method to produce the final index. The results of the aggregation indicated that the overall condition of water resources in Citarum catchment was considered poor, with a final index value of 20.04. Based on the WJWSI application, recommendations are suggested to the relevant authorities in the Citarum catchment. It is expected that the implementation of these recommendations will improve the performance of these five indicators and sub-indicators from Poor to at least the next higher level of Poor–Medium, thus improving the value of the final index from 20.04 to 37.19.