The application of biochar in agricultural ecosystems is emerging as a potential solution to mitigate nitrous oxide (N₂O) emission. However, the impact of biochar application on N₂O emissions from cropland appears to be variable among numerous studies and remains uncertain. Therefore, the effects of biochar application under oxygen conditions were comprehensively analyzed for countries similar to Korea. In this study, a dataset based on 42 published papers was used to quantify the effect sizes of biochar application on soil N₂O emissions. As a result of the meta-analysis, the N₂O reduction effect of biochar was 33.0 ± 15.0%, which was significantly reduced by 28.1 ± 2.0% under aerobic conditions and 37.5 ± 4.1% under anaerobic conditions (p < 0.001). As a result of a meta-analysis of related variables for N₂O emission, it was analyzed that the input amount of biochar, pyrolysis temperature, soil C/N, and fertilizer input had a significant N₂O reduction effect under both aerobic and anaerobic conditions. In this study, it was found that N₂O emissions could be reduced through the application of biochar in cropland of East Asia. The response ratio of N₂O was greater under anaerobic conditions, but quantitatively it was greater under aerobic conditions. This suggests that the biochar application effect will be high in aerobic conditions soil such as uplands.