Hydroxylamine (NH2OH) and hydrazine (N2H4) are crucial intermediates in biological nitrogen removal processes, but their potential effects on the nitrogen-related metabolic pathway during the sulfur-driven autotrophic denitrification (SDAD) process remain unclear and were thus explored in this work. The results of dedicated batch tests indicated that the accumulation ratio of NO2− was positively correlated with the NH2OH concentration, reaching 86.2 ± 2.6% at the NH2OH concentration of 2.0 mg-N/L, while it was barely affected by the N2H4 concentration. Furthermore, the joint inhibition of NH2OH and free nitrous acid led to the substantial accumulation of N2O (up to 32.9 ± 1.3%) during the NO2− reduction phase. In contrast, N2H4 exhibited great potential for facilitating N2O accumulation in both the NO3− reduction and NO2− reduction phases with an accumulation ratio of 13.0 ± 0.3% and 27.5 ± 1.5%, respectively, at the N2H4 concentration of 2.0 mg-N/L. Total enzyme activity analyses revealed that the presence of NH2OH inhibited the activity expression of all denitrifying enzymes, with the downstream enzymes (such as NO2− reductase and N2O reductase) being more susceptible to NH2OH. The addition of N2H4 did not cause a significant decrease in the activity of NO3− reductase and NO2− reductase, but notably curbed the activity of N2O reductase. Based on the responses of the SDAD-related nitrogen metabolic pathway to NH2OH/N2H4, this work provided effective technical means for i) the promotion of NO2− accumulation which might enable the coupling of SDAD with Anammox and ii) the efficient recovery of N2O via the SDAD process.