Reducing N2O emissions from agricultural soils without sacrificing crop productivity requires more than cutting inputs. It requires biological strategies that restructure the nitrogen cycle itself. Microbial inoculants, including rhizobia, endophytes, plant growth-promoting rhizobacteria, and arbuscular mycorrhizal fungi, affect soil nitrogen transformations in distinct ways. However, many reviews have considered these pathways in isolation or within narrow contexts. This review addresses that gap by building a unified framework that integrates five pathways through which microbial inoculants can reduce N2O emissions and improve nitrogen use efficiency: reducing inorganic nitrogen substrates available for nitrification and denitrification; outcompeting N2O-pro-ducing microorganisms; enhancing nosZ-encoded N2O reductase that completes denitrification to N2; synchronizing nitrogen supply with crop demand; and improving soil aggregate stability to limit anaerobic microsites. The literature reporting measured N2O fluxes and nitrogen-cycling functional gene abundances under microbial inoculation is synthesized, and the strength of evidence supporting each pathway is assessed. Co-inoculation strategies, greenhouse gas trade-offs, and formulation and persistence challenges are also evaluated. Field-integrated strategies that pair inoculants with reduced synthetic nitrogen inputs achieve more reliable reductions in synthetic nitrogen inputs. The nosZ-mediated pathway is the best-supported, with field reductions of 28-54% reported during post-harvest and nodule-decomposition periods, although reductions in annual cumulative emissions have not been demonstrated, and four of eight quantified studies concern soybean-- Bradyrhizobium systems alone. Factorial field trials that cross inoculants with contrasting amendment chemistries and integrate N2O fluxes across the full year should be prioritized. In practice, inoculants should be deployed as part of site-specific nitrogen management, combined with a concurrent reduction in synthetic nitrogen rates, matched to fertilizer form and soil pH, and applied where resident rhizobia lack nosZ, rather than as a standalone mitigation measure.