Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) is one of the most important polyphagous pests globally. It was reported in Brazil at the end of the 2012/2013 crop season. The aim of this study was to report the occurrence of an entomopathogenic fungus on H. armigera larvae in Brazil. We collected 589 larvae from cotton plantations in Bahia State, Brazil, and transported them to the laboratory of biological control of Embrapa Milho e Sorgo in Sete Lagoas, Minas Gerais State, Brazil. Of the 320 dead larvae, 106 were infected by Nomuraea rileyi (Farl.) Samson (Hypocreales: Clavicipitaceae), causing 33.1% of the total mortality. This is the first report on the natural occurrence of the fungus N. rileyi infecting H. armigera larvae in Brazil.