While the ocean is a critical regulator of atmospheric nitrous oxide (N2O) levels, its specific contribution remains poorly constrained. Here, we implemented an N2O module into the Estimating Circulation and Climate of the Ocean‐Darwin (ECCO‐Darwin) to investigate global sea‐air N2O fluxes, trends and interannual variabilities. From 1992 to 2017, the model yielded a global the oceanic N2O efflux of 2.43 ± 0.43 Tg N yr^-1, with a declining trend of ????0.021 ± 0.0031 Tg N yr^-2, attributed mainly to a reduction in N2O production induced by strengthened upper‐ocean stratification. The Eastern Tropical Pacific (ETP), Indian Ocean (IO) and Southern Ocean (SO) emerge as the primary three hotspots for N2O outgassing, where interannual variability is modulated by regional climate modes. In the ETP and IO, N2O fluxes strongly correlate with the El Niño Southern Oscillation index, with correlation coefficients of r = 0.93 and 0.53, respectively. During El Niño, reduced wind speeds and the deepening of the thermocline lead to decreased N2O outgassing in the ETP. El Niño events also tend to result in a positive Indian Ocean Dipole, which causes the thermocline in the Eastern Tropical IO to shoal, resulting in increased N2O outgassing. In the SO, the interannual variability of N2O fluxes is positively correlates with the Southern Annular Mode (SAM) index (r = 0.76). When the SAM is positive, westerly winds shift poleward, strengthening Ekman pumping and resulting in more subsurface N2O‐laden water being upwelled and outgassed. Our study provides a mechanistic understanding of the critical role of ocean‐atmosphere dynamics and climate variability in modulating oceanic N2O emissions.