Objective · To identify the effect and potential mechanism of gambogic acid (GA) on natural killer/T-cell lymphoma (NK/TCL) cell lines.  Methods · SNK-1, SNK-6 and SNT-8 were incubated with various concentrations of GA for 24 h, and cell viability was detected with CCK-8 assay. Cell apoptosis was examined by Annexin V-FITC/PI staining assay. Levels of proteins regulating cell apoptosis and phosphorylation levels of proteins in key signaling pathways were detected by Western blotting.  Results · GA showed a potent effect on reduction of cell viability of NK/TCL cell lines in CCK-8 assay. GA increased the percentages of Annexin V positive cells and induced activation of caspase-3 and caspase-9, cleavage of PARP as well as the reduction of Bcl-xl. GA also inhibited the phosphorylation levels of STAT3 in SNK-1 and SNT-8, and ERK1/2 in SNK-1 and SNK-6 significantly.  Conclusion · GA induces cell apoptosis in NK/TCL cell lines SNK-1, SNK-6 and SNT-8. Anti-apoptosis protein Bcl-xl and signaling pathway JAKs/ STATs and MEK/MAPK might be involved in this process.