Gallbladder carcinoma is the most common malignancy of the biliary tract and is associated with a very poor outcome. The aim of the present study was to investigate the effects of oxymatrine (OM) on gallbladder cancer cells and the possible mechanism of its effects. The effects of OM on the proliferation of gallbladder cancer cells (GBC-SD and SGC-996) were investigated using cell counting kit-8 and colony formation assays. Annexin V/propidium iodide double staining was performed to investigate whether OM could induce apoptosis in gallbladder cancer cells. The mitochondrial membrane potential (ΔΨm) and expression of apoptosis-associated proteins were evaluated to identify a mechanism for the effects of OM. In addition, the RNA expression of relevant genes was measured by qRT-PCR using the SYBR Green method. Finally, a subcutaneous implantation model was used to verify the effects of OM on tumor growth in vivo. We found that OM inhibited the proliferation of gallbladder cancer cells. In addition, Annexin V/propidium iodide double staining showed that OM induced apoptosis after 48 h and the ΔΨm decreased in a dose-dependent manner after OM treatment. Moreover, the activation of caspase-3 and Bax and downregulation of Bcl-2 and nuclear factor κB were observed in OM-treated cells. Finally, OM potently inhibited in-vivo tumor growth following subcutaneous inoculation of SGC-996 cells in nude mice. In conclusion, OM treatment reduced proliferation and induced apoptosis in gallbladder cancer cells, which suggests that this drug may serve as a novel candidate for adjuvant treatment in patients with gallbladder cancer.