Two field experiments were conducted during 2015 at DakLak province to study the effects of rhizobia and phosphate-solubilizing bacteria (PSB) on soybean (cv. Cujut) cultivated on ferralsols. In the first experiment was carried out at Centre for Agriculture Research, Western Highland Agricultural Institute (at Buon Ma Thuot city), consisted of five treatments as follows: control (no fertilizer, no inoculant), 400 kg/ha NPK 15-15-15, rhizobial inoculant [with liquid cover seeds] + 20 kg N/ha applied at 10 days after sowing [DAS], PSB inoculant [with liquid cover seeds] + 20 kg N/ha at 10 DAS, rhizobial and PSB inoculant [with liquid cover seeds] + 20 kg N/ha at 10 DAS from April to August, 2015. In the second experiment was carried out at Buonho town, consisted of four treatments as control (no fertilizer, no inoculant), 100 kg/ha thermophosphate (15% P₂O₅) + 25 kg/ha NPK 16-16-8 applied at 20 and 40 at DAS, rhizobial and PSB inoculant [with liquid cover seeds] + 200 kg biofertilizer + 20 kg N/ha at 10 DAS and rhizobial and PSB inoculant [with liquid cover seeds] + 400 kg biofertilizer + 20 kg N/ha at 10 DAS. The results showed that application of rhizobial inoculant and/or PSB inoculant produced significantly higher yield component, grain yield than control and did not differ from 400 kg/ha NPK 15-15-15 in the experiment 1. In the second experiment, using biofertilizer for soybean cultivation supported higher yield component, grain yield and oil, protein in seed than control and equivalent with treatment of 100 kg/ha thermophosphate (15% P₂O₅) + 25 kg/ha NPK 16-16-8. It therefore seems that biofertilizers can be considered as a replacement for part of chemical fertilizers in soybean cultivation on ferralsols.