Evaluating different environmental policy options requires extensive modelling of biophysical processes and attributes linked with metrics to measure the magnitude and distribution of societal impacts. An integrated ecosystem services assessment (IESA) has potential to provide salient, credible and legitimate information for environmental policy- and decision-makers. Here we present results of an IESA of the Murray-Darling Basin Plan, an Australian Government initiative to restore aspects of river flow regimes to improve the ecological condition of floodplains, rivers and wetlands in south-eastern Australia. The main outcome from the IESA is that the supply of most ecosystem services (ES) improves under Basin Plan policy and that these improvements have considerable monetary value. An IESA can provide actionable ecological, economic and social information for policy- and decision-makers. In the Basin Plan case the IESA was underpinned by hydrological scenarios that were input into ecological models and interdisciplinary integration across scales, values and variables.