The antifungal constituents from the heartwood of Calophyllum symingtonianum (bintangor bukit; Clusiaceae) were investigated. Methanol extracts, n-hexane-solubles, ethyl acetate-solubles and ethyl acetate-insolubles obtained from the heartwood of C. symingtonianum were subjected to antifungal assay against the brown-rot fungus, Gloeophyllum trabeum, and the white-rot fungus, Pycnoporus sanguineus. n-Hexane-solubles and methanol extracts showed the highest activity against G. trabeum, followed by ethyl acetate-solubles. n-Hexane-solubles showed the highest activity against P. sanguineus, followed by methanol extracts and ethyl acetate-solubles. Two major xanthones, 1,3,5-trihydroxy-2-(3-methylbut-2-enyl)xanthone (1) and 6-desoxyjacareubin (2) were isolated from ethyl acetate-solubles and n-hexane-solubles, respectively, and the structures of these compounds were determined. They were isolated for the first time from C. symingtonianum. Xanthones 1 and 2 were active against the both fungi and showed significantly high activity against G. trabeum and P. sanguineus, respectively. The activities of these antifungal xanthones were comparable to or higher than those of the positive control, glycyrrhizic acid dipotassium salt. The results suggested the significant potential of the heartwood of C. symingtonianum as a source of fungistats.