No negative effects on fruit quality is essential for the practical use of Beauveria bassiana as a substitute for methyl bromide in date fruits disinfection. Experiment was conducted in a completely randomized design with two level factorial arrangements. The first factor included three cultivars including Sayer, Zahed and Deiri and the second factor consisted of inoculation with fungal spores and control. The fruits of dates cultivar, Zahedi, Deiri and Sayer, were treated by doses of 5.21×10⁴ 2.46×10⁴ and 2.69×10⁴ spores/ml, respectively. The results showed that biopesticide treatment could not change the physiological characteristics of the fruits compared to the control. Although biopesticide treatment was effective in maintaining the quality of all studied date cultivars, it had the greatest effect on Deiri date cultivar. This method reduced the accumulation of sugar in the fruit. Absorption or loss of fruit moisture due to treatment was negligible. The concentration of soluble solids in the fruit extract was not affected by the treatment, but changes were observed in the three studied dates cultivars during the six months of storage, which indicates the importance of treatments to increase the length of the shelf life.