Climatic extremes and violent conflicts can play a significant role in reducing a country’s population. However, the occasional coexistence and interplay of climatic extremes and violent conflicts make it difficult to quantify their individual or collective demographic impacts and associated spatial dynamics, and thus to determine which plays the more important part. Can long-term historical data shed more light on this conundrum? This study explores the effect of climatic extremes and violent conflicts on China’s population, using data from 1741 to 1910 and spatial econometrics. It differs from other quantitative historical studies by addressing the spatial autocorrelation property of population data and the spatial spillover effect of those population-determining factors. The statistical results show that, in general, violent conflicts reduce population density, and that their demographic impact is stronger than those of climatic extremes. Specifically, while violent conflicts reduce population density in the areas they directly affect, they also increase the population density in neighboring areas, as people flee the affected area and take refuge elsewhere. Alternatively, floods, droughts, and extreme floods cannot suppress the local population density but negatively affect the population density in the surrounding areas. Furthermore, violent conflicts and extreme droughts have a significant synergistic effect in reducing population density. This study provides a more detailed picture of the impact of climatic extremes and violent conflicts on historical population densities, and draws attention to the nuanced spatial dynamics embedded in the nexus between the population and its determinants. More generally, its findings may help future researchers to determine the demographic impact of more frequent climatic extremes and violent conflicts brought on by global climate change.