Several chemical substances are used to control insects, diseases and weeds; however many of these are toxic to mankid and the animals besides reducing the potential of pest control by predators, parasitoids and pathogens. Because biopesticides are thought to be more rapidly degradable than synthetic chemicals while having a lower ecotoxicological effects, the interest in these products for pest control has grown substantially. The insecticidal activity of an isolate local strain of an entomopathogenic fungus, Metarhizium anisopliae (Metsch) Sorok, was tested at four doses, against fourth larval stage and adults (male & female) of Ceratitis capitata (Wied) under laboratory conditions. The percentage of accumulated mortalities of the fourth larvae at the seventh day after inoculation were 26.13% for the lower dose, 6.5 x105spore/ml and increased to 89.05 for the highest dose represented by 52 x 105 spore/ml. Obtained results showed that the susceptibility of males to the fungus was higher the females with mortality of 88.21% and 76.05 respectively with the of 52 x 105 spore/ml. These toxicity assays allowed the determination of the different lethal doses (CL50, CL90) for both stages. The assay of the female adult of C. capitata exposed to DL50 = 25.4 x105; DL90 = 68.6 x105 spore/ml) of M. anisopliae showed a significant decrease (p<0.05) of the egg number laid after treatment. The cuticular proteins amounts have been were determined on the fourth instar larvae of C. capitata at 3 and 6 days after treatment with the two lethal doses (DL50=24.8 x105; DL90= 49.6 x105 spore/ml). Results showed a significant decrease in protein amounts after treatment as compared to control series. The bioassays reveal that Metarhizium anisopliae presents better potential for the biological control of Ceratitis capitata.