The objective of the present study was to investigate the effect of two wheat cultivars (the Sirvan and Mihan) on the interaction between Beauveria bassiana strain EUT116, Rhyzopertha dominica and Tribolium castaneum at 25± 1°C, 85±5% RH and darkness. The results of bioassay by submersion method showed that the lethal concentrations and times of the fungus were significantly different between the Sirvan and Mihan. The mortality of R. dominica was significantly lower on the Mihan infected with a dose rate of 1 g/kg than the Sirvan. The mortality of Rhyzopertha dominica was remarkably higher for the adults exposed to the dose rate of 1 g/kg than the adults exposed to 0.25 g/kg. The mortality of Tribolium castaneum was remarkably higher for the adults were exposed to the dose rate of 1 g/kg than the adults were exposed to 0.25 g/kg. The highest mortality occurred for R. dominica infected with 1 g of B. bassiana per kg of the Sirvan. The pathogenicity of dose rate 1 g/kg on the Sirvan was higher against R. dominica than T. castaneum. The 0.25 g of B. bassiana per kg of the Mihan differentially caused higher mortality on R. dominica than T. castaneum. It seems that planting the Sirvan cultivar in the field can be more helpful to decrease the population of stored grain beetles rather than the Mihan in post-harvest conditions. According to our results, B. bassiana strain EUT116 was a promising candidate as a biocontrol agent to suppress the storage grain beetles, especially, R. dominica.