Phosphate solubilizing bacteria (PSB) have an ability converting insoluble forms of phosphorus to an accessible form. The study was conducted to investigate how bacterial inoculation to unfertilized sunflower (Helianthus annuus L.) or fertilized with phosphorus affected seed set and filling efficiency, kernel yield and chemical composition of seed under field conditions. Study plots were treated with two levels of P-solubilizing Bacillus M-13 bacterium (Control and PSB) and three levels of phosphorus fertilizer (0, 50 and 100 kg P2O5 ha-1 ) with three replications. Applications of PSB significantly increased seed set (8.2-20.0%), seed filling efficiency (1.3-1.9%), kernel yield (37.3-67.0%) and quality by reducing hull percentage (15.2- 24.3%) and by improving nutrient concentrations of seeds. It was concluded that application of 50 kg ha-1 dose of P fertilizer with PSB can give similar seed set and kernel yield as with 100 kg ha-1 dose of P fertilizer. Besides, PSB application caused a substantial increase in all macro-and micronutrients in seeds. In conclusion, application of P-solubilizing bacteria with or without P fertilizer leads to increase in seed set and kernel yield and alteration in nutrient concentrations in the seeds of sunflower plant.