The aim of this study is to investigate whether HJC, isolated from Justicia procumbens for the first time, can suppress the proliferation and induce apoptosis of human leukemia K562 cells and finally clarify its related mechanism. The chemical structure of HJC was validated by LC-ESI-MS/MS, cytotoxicity was assayed using MTT, and apoptosis was investigated by flow cytometry. These assays indicated that HJC remarkably inhibited the growth in K562 cells by decreasing cell proliferation, reducing the SOD activity, enhancing ROS levels and inducing apoptosis. Activation of caspase-3 indicated that HJC may be inducing intrinsic and extrinsic apoptosis pathways and that HJC-induced apoptosis was caspase-dependent. This study suggests that HJC is a high-potency anti-tumor agent, and it induces apoptosis through a caspase-dependent pathway in human leukemia K562 cells. It also presents a potential alternative to leukemia therapy.