Lakes are emission hotpots of nitrous oxide (N2O), however, this phenomenon remains poorly constrained. Eutrophication is widespread in lakes, yet its contribution to N2O emissions is still not well understood. Here, we investigate the spatiotemporal variations of N2O concentrations, fluxes and indirect emission factors (EF5r) and their drivers in Ulansuhai lake, a shallow eutrophic lake located in a semi-arid region in northern China, during 2019-2020. The mean concentration of N2O in water was 20.0 +/- 6.7 nmol/L, with a mean diffusive N2O flux of 16.50 +/- 21.52 mu mol/(m(2)day), indicating that this lake acted as a persistent source of atmospheric N2O. Estimated indirect emission factors (EF5r) (mean value 0.0037 +/- 0.0060) were significantly higher than the default values (0.0026) used in Intergovernmental Panel on Climate Change (IPCC) emission inventories. The N2O concentrations, fluxes and EF5r exhibited substantial seasonal variations and small spatial variations. N2O concentrations and fluxes were positively correlated with the trophic status and EF5r increased with increasing nutrient concentrations in the water. These findings demonstrate the role of eutrophication in influencing the N2O dynamics and confirm that eutrophication can exacerbate N2O emissions.