Two new polycyclic prenylated xanthones (1 and 2) and a new phenylpropanoid glycoside (3), along with seven known compounds (4-10) were isolated from the fruits of Garcinia xanthochymus. The structures were elucidated by 1D- and 2D-NMR, and HRMS experiments. The isolates were evaluated for their inhibitory effects against the viability of U251MG glioblastoma and MDA-MB-231 breast cancer cells that harbor an aberrantly active signal transducer and exhibit activation of transcription 3 (STAT3), and compared to normal NIH3T3 mouse fibroblasts. Among the isolates, compounds 1, 2, 5, and 6-9 inhibited the viability of glioma cancer cells with IC50 values in the range of 1.6-6.5μM. Furthermore, treatment of U251MG with 6 and 7 inhibited intracellular STAT3 tyrosine phosphorylation and glioma cell migration in vitro, respectively.