Entomopathogenic fungi can play an important role as key biocontrol agent of agricultural pests’ population. The present research aimed to test the effectiveness of Beauveria bassiana Vuill. (Hypocreales: Cordycipitaceae) strains against Tettigonia viridissima L. (Orthoptera: Tettigoniidae). In laboratory conditions study, the impact of different B. bassiana strains 214, 644, and 733 on green grasshoppers’ larvae were determined. The enzyme activities (proteolytic, lipolytic, and chitinase) and the presence of the chitinase (chit1) gene in the studied strains of B. bassiana (214, 644, and 733) were also analyzed. As a result, it was found that all three tested strains exhibited proteolytic, lipolytic and chitin-degrading activity and amplified fragments with the expected length. It was also found that all the strains were effective on T. viridissima. The highest effect of the tested strains was found by strain 214 – 66.7%, followed by strains 644 – 55.6% and stains 733 – 44.4% on the 4th day after treatment. Effectiveness gradually increased and on the 7th day after treatment, mortality was found on 100% green grasshoppers’ larvae. Although different effectiveness between strains 214, 644, and 733 was found on the 4th day after the test, the differences were not significant between the strains. The research shows the possibility of successful utilization of B. bassiana strains for controlling T. viridissima.