Background: Multiple myeloma (MM) is one of the most common primary tumors of the bone marrow that accounts for approximately 10% of all hematological cancer. Gambogenic acid (GNA) is one of the natural compound isolated from gamboge and has demonstrated advantages such as a more potent anticancer effect and less systemic toxicity according to early investigations. In this study, we hypothesized that GNA could synergistically potentiate BTZ-induced apoptosis of MM cells and that combining BTZ and GNA may provide a more effective approach to treat MM. Methods: CCK-8 assay, CI isobologram, flow cytometry, western blot, xenograft tumour models, TUNEL and immunochemistry were used in this study to detect to possible mechanisms of apoptosis led by GNA and BTZ in vitro and in vivo. Results: The percentage of MM.1S in G2/M phase after 48h of 4.0nM BTZ, 0.90μM GNA and combination treatment were 31.09±2.16%, 26.68±1.96% and 19.88±1.89% respectively. The percentage of MM.1S in G2/M phase of control group was 17.23±1.65%. The apoptosis rates of MM.1S cells for 48h were 6.57±0.15% in control group, 89.67±5.15% after treatment with 4.0nM BTZ, 97.80±0.81% after treatment with 0.90μM GNA, and 98.9±3.86% after treatment with 4.0nM BTZ plus 0.9μM GNA respectively. All the treatment groups showed a more significant apoptosis rate compared to that of the control group (p<0.01). MM.1S tumors were implanted in BALB/Ca nu/nu male mice. The tumor weights of GNA and BTZ plus GNA groups decreased significantly when compared with those of control group (p<0.01 and p<0.001, respectively) and the tumor weight of combination group was significantly less than that of BTZ or GNA group (p<0.001). When mice were treated with BTZ combined with GNA, the tumor inhibition rate was 41.94%, whereas those of mice treated with BTZ or GNA alone were 9.68% and 19.35%, respectively. We also found that the combined treatment could induce more markedly increased apoptosis of MM.1S cells via the activation of PARP cleavage, P53, Caspase-3 cleavage and Bax and inhibition of Bcl-2 expression. Conclusions: Our data support that a synergistic antitumor activity exists between BTZ and GNA, and provide a rationale for successful utilization of dual BTZ and GNA in MM chemotherapy in the future.