A new flavone, 3-methoxy-5-hydroxy-[2",3":7,8] furanoflavone, pubinerone (1), was isolated from the twigs of Millettia pubinervis Kurz, together with ten known flavonoids, karanjin (2), kanjone (3), 3,6-dimethoxy-[2",3":7,8] furanoflavone (4), pongaglabrone (5), pongapin (6), pongaflavone (7), 3,6-dimethoxy- 6",6"-dimethylchromene-[2",3":7,8] flavone (8), pongachromene (9), 3,6-dimethoxy-3',4'-methylenedioxy-6",6"-dimethylchromene-[2",3":7,8] flavone (10) and demethoxykanugin (11). This is the first phytochemical investigation of this plant. The structure of compound 1 was elucidated on the basis of spectroscopic data interpretation, including 1D and 2D NMR and HREIMS analysis. The cytotoxicity of 1 against five human cancer cell lines; HL-60, SMMC-7721, A-549, MCF-7 and SW480, was evaluated, but it was inactive (IC50 > 40 μM).