The fall webworm, Hyphantria cunea (Lepidoptera: Arctiidae) is a dangerous and destructive pest for forest, fruit trees and ornamental plants. Insecticides are successful to reduce population of this pest, but they cause environmental pollution. In this study, the virulence efficacy of M. anisopliae was determined on the fourth instar larvae of H. cunea under laboratory conditions. 1×10⁶ and 1×10⁸ conidial suspensions of M. anisopliae grew at 20, 25 and 30°C temperatures. 1×10⁸ conidial suspensions of M. anisopliae were the most efficacious in controlling larvae of H. cunea at spraying method, especially at 30°C with 100 % mortality after 9 days of treatment. 1×10⁸ conidial suspensions of M. anisopliae more efficacious in controlling larvae of H. cunea at 20 and 25°C (63% and 84%) than 1×10⁶ conidial suspensions of M. anisopliae at 20, 25 and 30°C (34%, 46% and 72%) after 9 days of treatment. This study showed that isolate of M. anisopliae has virulent and highly potential for biological control on larvae of H. cunea.