A few studies have shown that amine compounds (e.g., hydroxylamine) can be co-metabolically introduced into the reaction pathway of denitrification. During this microbial process, the N atom of the amine species is bound to a N atom of nitrite. In case of hydroxylamine, this concomitant reaction ultimately results in the formation of hybrid N₂O. Due to its co-metabolic character the process has been termed co-denitrification. Hybrid N₂O production during co-denitrification has been proven to occur in prokaryotic (e.g., Pseudomonas sp.) as well as eukaryotic (e.g., Fusarium sp.) species. Many of them are already well-known as common denitrifiers. However, until now no clear evidence has been provided to show that N₂O production by co-denitrification really takes place in a soil. In the present study, a formation of hybrid N₂O was revealed by an adapted ¹⁵N-tracer model, when both hydroxylamine and ¹⁵N-nitrate were applied (mol ratio 10:1) to an anaerobically incubated soil suspension from a Haplic Chernozem. The presence of hybrid N₂O was also indicated by a novel characteristic factor (R_binom) developed for a hybrid-N-N-gas detection. By contrast, no hybrid N₂O was found when either an autoclaved soil suspension, only nitrate or only hydroxylamine was used. Thus, it appears that hybrid-N₂O formation occurred due to co-denitrification of hydroxylamine. Hence, this is the first study which demonstrates hybrid-N₂O production by co-denitrification beyond a microbial species level. The ¹⁵N-tracer model revealed that under the given experimental conditions N₂O production by co-denitrification prevailed against N₂O from denitrification and abiotic hydroxylamine decomposition. In addition, a formation of hybrid N₂ was also calculated by the model. However, the experimental results lead to the conclusion that it was most likely caused by a reduction of hybrid N₂O due to conventional denitrification.