AbstractTemporal changes in the magnitude and geographic distribution of different sources of nitrous oxide (N₂O) are not well constrained. To better understand the dynamics of N₂O in the atmosphere over the last century, we have reconstructed the mole fraction, δ¹⁵N^bulk, δ¹⁸O, and δ¹⁵N^SP values of N₂O from ice cores, firn air archives, and modern atmospheric samples. We have provided new firn air records from the Styx Glacier, Antarctica, and the North Greenland Eemian Ice drilling Project, and updated the firn air transport modeling of the published records. The composite reconstruction shows that the N₂O growth rates were 0.26 ± 0.05, 0.15 ± 0.05 and 0.75 ± 0.01 ppb yr⁻¹ during 1850–1930 (P1), 1931–1965 (P2) and 1966–2021 CE (P3), respectively. The temporal slope found in a linear least squares fit in δ¹⁵N^bulk and δ¹⁸O were −0.010 ± 0.025 and −0.004 ± 0.031‰ yr⁻¹, −0.014 ± 0.013 and −0.009 ± 0.017‰ yr⁻¹, and −0.040 ± 0.013 and −0.022 ± 0.005‰ yr⁻¹ during P1, P2 and P3 phases, respectively. Overall, a significant long‐term trend was not observed in δ¹⁵N^SP data. Two‐box model calculations using N₂O mole fraction suggest that the total N₂O flux (F_T) at 2015 CE was 17.5 ± 1.1 TgN yr⁻¹, where flux from the natural (F_N) and anthropogenic (F_A) sources were ∼60% and 40% of F_T, respectively, and the contribution of F_A was ∼30% of F_T at 1900 CE. Estimated F_A and δ¹⁵N^bulk of atmospheric N₂O suggest that the anthropogenic emissions from continental regions were 12%, 25% and 76% of F_A during P1, P2 and P3 phases, respectively.