A field experiment was carried out in the farm of faculty of Agriculture, Mansoura University, Mansoura, Egypt during the winter season of 2016 to study the effect of bio-fertilization under different level of nitrogen (75% and 50% of the full dose) on the growth and yield of wheat plant. Obtained results showed that the microbial inoculation leads to a significant increase in growth parameters (plant heights, number of tillers, leaves and dry weights). Also, microbial inoculation leads to a significant increase in NPK-contents as responded to all treatments under investigation in all stages of plant growth. The obtained results show a significant increase in yield parameters and its components (spike length, spike weight , number of grains / spike, weight of 1000 grains, grain and straw yield and NPK contents in grains and straw) as affected by microbial inoculation. The treatment T 9 (Az. chroococcum + K. oxytoca + 75 % dose of N) gave the highest value of grains and straw yield (19.61 and 3.13 ton/fed., respectively) with an increase by 21.87% and 19.01%, respectively. Also, the bio-fertilization has a pronounced increase in microbial count in comparison with the mineral fertilization. The present study recommend by the possibility of using the dual bacterial inoculum which containing Azotobacter chroococcum MF135558 and Klebsiella oxytoca MF135559 in the presence of 75% dose of N for enhancing growth and yield of wheat plants and reduce chemical fertilizers usage.