Two perinaphthenone-type compounds (1 and 2) were isolated together with four known phenylphenalenones (3−6) from the rhizomes of Musa acuminata var. "Yangambi km 5". The structures of the new phenalenones were assigned as 2-hydroxy-1H-phenalen-1-one (1) and 2-methoxy-1H-phenalen-1-one (2) on the basis of their spectroscopic data and were confirmed by synthesis. Compounds 1 and 2 displayed significantly enhanced activity against Mycosphaerella fijiensis in comparison with other phenylphenalenones.