This investigation were carried to test effect of mealy bug infestation and two inoculation methods of the entomopathogenic fungal endophyte, Beauveria bassiana to cotton plant, Gossypium barbadense L. (var. Giza 90) on some chemical component of cotton plant. The change in growth photosynthetic pigment content, total protein content, total antioxidant capacity total flavonoid content and the activities of some antioxidant were determined. Results showed that, B. bassiana treatments could induce the length and weight of fresh stem. Pest infestation and/or B. bassiana treatments, an increase in the amounts of flavonoids was noticed as compared to the control while B. bassiana application caused decrease in the antioxidant activity of leaf extracts detected by DPPH assay. Cotton plants showed accumulation in total proteins as a defense mechanism against Phenacoccus solenopsis (Tinsley) treatments.