Climate change and nutrient pollution are among the most urgent environmental issues. Enhancing the abundance and/or the activity of beneficial organisms is an attractive strategy to counteract these problems. Dissimilatory nitrate reduction to ammonium (DNRA), which theoretically improves nitrogen retention in soils, has been suggested as a microbial process that may be harnessed, especially since many DNRA-catalyzing organisms have been found to possess nosZ genes and the ability to respire N2O. However, the selective advantage that may favor these nosZ-harboring DNRA-catalyzing organisms is not well understood. Here, the effect of N2O on Nrf-mediated DNRA was examined in a soil isolate, Bacillus sp. DNRA2, possessing both nrfA and nosZ genes. The DNRA metabolism of this bacterium was observed in the presence of C2H2, a NosZ inhibitor, with or without N2O, and the results were compared with C2H2-free controls. Cultures were also exposed to repeated oxic-anoxic transitions in the sustained presence of N2O. The NO2 −-to-NH4 + reduction following oxic-to-anoxic transition was significantly delayed in NosZ-inhibited C2H2-amended cultures, and the inhibition was more pronounced with repeated oxic-anoxic transitions. The possibility of C2H2 involvement was dismissed since the cultures continuously flushed with C2H2/N2 mixed gas after initial oxic incubation did not exhibit a similar delay in DNRA progression as that observed in the culture flushed with N2O-containing gas. The findings suggest a possibility that the oft-observed nosZ presence in DNRA-catalyzing microorganisms secures an early transcription of their DNRA genes by scavenging N2O, thus enhancing their capacity to compete with denitrifiers at oxic-anoxic interfaces.