Laboratory experiments were carried out to de-termine the bioeffects of an isolate of ento-mopthogenic fungi Beauveria bassiana (Bals.) and Biofly a commercial product of B. bassiana, on the 1st instar larvae of mushroom fly, Bradysia ocellaris (coms). The bioactivity of B. bassiana was tested, using five concentrations of B. bassi-ana on some biological criteria of the mushroom fly, by calculating LC50 values after three and sev-en days of treatment. Results indicated that the mortality rates percentage increased with the in-crease of the concentrations used and the period after treatment. The highest percentage of mortali-ty occurred within the first seven days following treatment. Statistical analysis of the obtained lar-val-pupal and adults period and weight revealed significant differences between treated and non-treated insects.