Nutrient delivery and water yield are key ecosystem functions that impact food security. Climate and Land Use land Cover (LULC) changes are the main driving factors that affect these water-related ecosystem services. By recognizing the value of ecosystem services, the efforts to manage ecosystem services have increased. One such tool to help manage ecosystem services is the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, a new but powerful ecosystem service model. However, the InVEST model still requires testing in various geographic regions. This study assessed the performance of the InVEST water yield model in Siem Reap Province, Cambodia. The climate scenarios were projected using CMIP6 for two pathways, namely SSP2-4.5 and SSP5-8.5. Past, Present, and future scenarios were developed for two InVEST models including annual water yield (AWY) and nutrient delivery ratio (NDR) to evaluate the impacts of climate change and LULC. For the past and present scenarios, it was observed that the water yield has decreased by 52–69% from 2018 to 2022 and nitrogen and phosphorus exports have increased by around 627 and 186 tons, respectively. For the future scenarios, it has been observed that from SSP2-4.5 to SSP5-8.5 scenario, the water yield has decreased in NF by 6–8%, for MF it has increased by 10–12% and for FF scenario it has again decreased from around 1 to 2%. In addition to that, for the future scenarios, there was slight variation in nutrient delivery from SSP2-4.5 to SSP5-8.5 scenario. Nitrogen exports decreased by 0.42 tons for NF, and slightly increased by 3 tons for MF, also slightly increased by 2.4 tons for FF scenario. Whereas phosphorus exports decreased by 0.07 tons for NF, and slightly increased by 0.8 tons for MF, also slightly increased by 0.7 tons for FF scenario in Siem Reap province. Hence, it can be concluded that climate change plays a dominant role in affecting water yield, while LULC plays a dominant role in affecting nutrient delivery.