A new geranylated xanthone derivative, fuscaxanthone I (1), along with nine xanthones (2-9 and 11), a biphenyl (10) and three biflavonoids (12-14) were isolated from the roots of Garcinia fusca Pierre. Compounds 8, 10 and 11-14 were reported from this plant species for the first time. Their structures were elucidated by spectroscopic analyses, including 1D- and 2D-NMR and MS. The isolated compounds were evaluated for antibacterial activity against Helicobacter pylori. Cowaxanthone (5) and fukugiside (14) exhibited stronger inhibitory activity against H. pylori DMST reference strain at MICs 4.6 and 10.8 μM, respectively, than that of the control metronidazole. Isojacareubin (8) displayed the most potent activity against H. pylori HP40 clinical isolate with MIC 23.9 μM, which was approximately two times greater than that of the standard drug amoxicillin.