In the course of screening for new biologically active compounds from saprophytic fungi on plants, a new antifungal alkaloid named fungerin was isolated from a Fusarium sp. fungus (isolated from a stalk of Miscanthus sacchariflorus). The producing organism was determined to belong to the Fusarium genus. Fungerin was obtained via fermentation, extraction, and chromatography. Its structure was elucidated principally by NMR spectroscopy involving 15N-NMR studies using the pulsed field gradient (PFG)-HMBC technique at natural abundance, and was determined to be 3-[1-methyl-5-(3-methyl-2-butenyl)-1H-imidazol-4-yl]-2(E)-propenoic acid methyl ester as a new alkaloid. Fungerin showed antifungal activities against Penicillium chrysogenum, Colletotrichum langenarium, Alternaria mali IF08984, and Pyricularia oryzae IF05994 with MIC values of 12.5, 25, 50, and 50 µg/ml respectively, but no antibacterial activities.