Abstract: Background and Objective: Variability in symbiotic effectiveness of soybean varieties to inoculation and phosphorus supplementation have not been fully explored. The aim of this study was to assess the comparative effects of Bradyrhizobium japonicum inoculant and single super phosphate (SSP) on growth and yield parameters of three improved soybeans genotypes. Materials and Methods: A field trial was conducted at the Teaching and Research Farm of the University of Agriculture Makurdi, Nigeria during the rainy season in 2017. The experiment was laid out in a split plot design with three soybeans genotypes constituting the main plot and the inoculant and SSP in the subplot. The inoculant and SSP were incorporated into the soil at planting. Results: Results showed that under main effects of fertilization types, inoculation with Bradyrhizobium japonicum, irrespective of variety gave the highest biomass per plant (13.61 g) and grain yield of 3.44 t ha–1 while nodules and root weights were statistically higher under SSP fertilization. All varieties performed best under P fertilization across all parameters measured, although there was significant variability in P responses by individual varieties. However, the interaction of TGX 1904-6f and inoculation gave the highest grain yield of 4.62 t ha–1, which indicated higher symbiotic effectiveness between this variety and Bradyrhizobium japonicum. Conclusion: Symbiotic effectiveness, P requirement and yield of soybeans varied among the different varieties and variety interaction with inoculation had the highest yield. Although P remained the major requirement for overall soybean productivity.