The chemical constituents of the fruits of Artocarpus altilis were investigated. The dried powdered whole fruit (900 g) was defatted with n-hexane and extracted with ethyl acetate and methanol. Twelve compounds, including stilbenes (1-3), arylbenzofuran (4), flavanone (5), flavones (6-8), triterpenes (9-10), and sterols (11-12), were isolated and identified by spectroscopic methods (EI-/FAB-MS, ¹H/¹³C NMR) and comparison with literature data. Compounds 2, 6, 9, and 12 were isolated from this plant for the first time. Compounds 1-4 exhibited significant antifungal activity against Cladosporium cladosporioides (MIC 10-20 μg/spot) and strong antioxidant activity against DPPH radical (IC50 2-10 ppm). Compound 4 showed cytotoxicity against Artemia salina (LC50 25 ppm) and phytotoxicity against Lactuca sativa (100% shoot growth inhibition at 250 ppm). Chemotaxonomically, compounds 1-8 possess the characteristic 2,4-dioxygenation pattern, which can serve as taxonomic markers for the family Moraceae, especially the genus Artocarpus.