Five new flavonoids, 5,8-dihydroxy-3,7-dimethoxy-3′,4′-methylenedioxyflavone (1), 7-hydroxy-3,5-dimethoxy-3′,4′-methylenedioxyflavone (2), 7-(2,3-dihydroxy-3-methylbutoxy)-3,5-dimethoxy-3′,4′-methylenedioxyflavone (3), 7-(2,3-dihydroxy-3-methylbutoxy)-3,3′,4′,5-tetramethoxyflavone (4), and 7-(2,3-dihydroxy-3-methylbutoxy)-3,3′,4′,5,8-pentamethoxyflavone (5), were isolated from the leaves of Melicope triphylla. In addition, six known flavonoids were detected: 3,4′,5-trihydroxy-3′,7,8-trimethoxyflavone (6), 5,7-dihydroxy-3-methoxy-3′,4′-methylenedioxyflavone (7), 4′,5,7-trihydroxy-3,3′-dimethoxyflavone (8), 4′,7-dihydroxy-3,3′,5,8-tetramethoxyflavone (9), 4′,7-dihydroxy-3,3′,5-trimethoxyflavone (10), and 4′,5,7-trihydroxy-3,3′,8-trimethoxyflavone (11). The new compound structures were determined by spectroscopic methods. Compounds 1–5 did not exhibit any ichthyotoxic activity against Japanese killifish (medaka in Japanese) (Oryzias latipes var.) at 10 ppm.