Fungi living within a plant (i.e., endophytic fungi) can directly affect the growth of the host plant or have indirect effects by affecting levels of damage to the plant caused by insect herbivory or plant pathogens. Greenhouse and field trials were conducted to investigate the endophytic effects of the fungus Beauveria bassiana on wheat, on the wheat-feeding Sunn pest, Eurygaster integriceps (Hemiptera: Scutelleridae), and on the wheat pathogen, Fusarium culmorum (Nectriaceae), which causes root and crown rot disease. Conidia of B. bassiana were applied to wheat either by foliar spray, soil drench, or seed treatment. Seed treatment with conidia provided the highest re-isolation percentages: 91.7% in leaves, 95.8% in stems, and 91.7% in roots. Inoculated plants were taller and had greater wet and dry weights compared to control plants. In both greenhouse and field studies, E. integriceps that were fed inoculated plants laid eggs that were less likely to hatch. Inoculations reduced the incidence of root and crown rot disease by 42% under greenhouse conditions. These results document the potential of using endophytic infections of B. bassiana in wheat as a control measure for Sunn pest and root and crown rot disease.