Both mammalian tensin-like phosphatase 1 [TEP1; also known as phosphatase deleted on chromosome 10 (PTEN) or mutated in multiple advanced cancer 1 (MMAC1)] and Saccharomyces cerevisiae ScTep1p are involved in the phosphatidylinositol pathway. In this study, we identified the Fusarium graminearum locus FGSG_04982.3 (named FgTEP1) as the functional homologue of ScTEP1 in the sensitivity of S. cerevisiae cells to wortmannin, the phosphatidylinositol-3 kinase inhibitor. Deletion of FgTEP1 causes F. graminearum mycelial growth to become sensitive to lithium and reduces the production of conidia. Although conidia lacking FgTEP1 germinate normally, they show reduced germination efficiency in the presence of wortmannin. In addition, we showed that deletion of FgTEP1 reduces the virulence of F. graminearum on wheat. These results indicate that FgTep1p is linked to the phosphatidylinositol-3 kinase signalling pathway in this plant fungal pathogen.