The objectives of this study were to determine the effects of combining nitrogen (N)-fixing bacteria and reduced nitrogen fertilizer on the growth, rice yield, and soil quality in the triple rice cultivation in the Vietnamese Mekong Delta region. The field experiment was arranged in a split-plot design, with the method of inoculating rice seeds with Gluconacetobacter diazotrophicus as the main factor and N fertilizer rates as the sub-factor. Two methods for rice seeds included: No inoculation with G. diazotrophicus (G0) and inoculation with G. diazotrophicus (Gd). Four N fertilizer rates included: no N fertilizer (N0), 50 kg N ha–1 (N50), 75 kg N ha–1 (N75), and 100 kg N ha–1 (N100). The results indicated that the combination of N-fixing bacteria and reduced N fertilizer could maintain the number of tillers, rice height, soil plant analysis development (SPAD) index, rice biomass, and grain yield (p>0.05). Additionally, the application of G. diazotrophicus or reduced N fertilizer did not significantly affect soil pH, electrical conductivity, soil organic matter, total N, and NH4+-N at the harvest stage. However, combining G. diazotrophicus with reduced N fertilizer resulted in a significantly improved soil pH, soil organic matter, NH4+-N, and available phosphorus compared to the treatment without G. diazotrophicus and treatment applied 100 kg N ha–1. The findings from this research provide a foundation for further study of applying the G. diazotrophicus to rice cultivation to reduce the N fertilizer, increase rice yield, and improve soil quality.