Analysing the financial sustainability of local governments is of great interest, as they offer a wide range of services and are close to citizens. Various organizations have pointed out the need to analyse the determinants of financial sustainability, and recent research has focused on several European countries, using adjusted income as a dependent variable. To fill the research gap in the context of German local governments, we conduct an empirical analysis with 5 years of data from 363 local governments from North Rhine–Westphalia to analyse the impact of socio-demographic and financial-economic factors on financial sustainability, focusing on the adjusted income. Our results indicate that financial sustainability is influenced by factors on which the local governments have no impact or at least only a limited impact. Specifically, the debt level and the level of population are identified as risk factors, whereas own taxes, rate support grants and the net cash surplus serve as drivers of financial sustainability. Points for practitioners Understanding the determinants of financial sustainability is important for politicians and public managers in order to improve their risk management and decision-making processes and to prevent future sustainability problems. This paper identifies several socio-demographic and financial-economic determinants of FS, on which the local governments have only a limited impact. Considering that the financial sustainability of German local governments in North Rhine–Westphalia largely depends on external factors might be of great interest for policymakers with regard to future financial crises.