Phytochemical analysis of a crude ethyl acetate (EtOAc) extract derived from endophytic fungus Fusarium verticillioides strain WF18 afforded one new polyketide metabolite, fusaisocoumarin A (1), along with two known compounds, emodin (2) and sesquiterpenoid phytohormone (+)-abscisic acid (ABA) (3). Chemical structures of isolated compounds were elucidated based on HRESIMS together with 1Dand 2D-NMR spectroscopic analyses. Interestingly, all isolated compounds revealed pronounced antifungal activity against certain endophytic fungal strains namely; Aspergillus austroafricanus strain Eis.1, Aspergillus versicolor strain EIS2, Phoma fungicola strain AT100, Aspergillus tubingensis strain AN103 along with Candida albicans ATCC 90029 with MIC (minimum inhibitory concentration) range from 0.3 to 1.3 mu g/mL. The biosynthesis of anti fungal compounds and the phytohormone (+)-abscisic acid (ABA) illustrates an example of the crosstalks between the host plant and its endophyte in which the endophytic fungus produces metabolites defending the host plant against environmental stresses and also against other fungal phytopathogens. (C) 2020 SAAB. Published by Elsevier B.V. All rights reserved.