The present study was carried out to investigate the pathogenicity of the fungus Beauveria bassiana when diluted in triton X100 at concentrations of 106, 107, 108, 109, and 1010 conidia/ml and sprayed on the eggs of the tick Argas persicus. For each concentration, three replicates were made (each included about 10–16 eggs). Scanning electron microscopy was used to examine the surface morphology of the eggs and their eclosing larvae after treatment with a selected concentration of 107 conidia/ml B. bassiana. Biological studies revealed that all treated eggs demonstrated a delay in the hatching period (a highly significant increase) and a marked decrease in the hatching percentage, which increased as fungal concentrations increased, reaching 30 days (p < 0.001) and 2.9%, respectively, using 108 conidia/ml. Total inhibition of both parameters was observed at higher concentrations (109 and 1010 conidia/ml). Scanning electron microscopy of the eggs after using a concentration of 107 conidia/ml, revealed signs of fungal adhesion 2 days after treatment, whereas germination occurred after 7 days. Excessive conidiogenesis and sporulation on the egg surface were observed after 15 days of treatment. All eclosing larvae appeared paralyzed 1–4 days after hatching with many conidia covering their whole bodies. The findings suggest that the fungus affected tick larvae are either directly infected in the eggs or indirectly during eclosion.