For millennia, traditional Chinese medicine (TCM) practitioners have treated cancer with Chinese medicinal herbs (CMHs), which continue to be used in combination with conventional chemotherapy and radiotherapy in contemporary oncologic care in Asia. Recent advances in biochemistry and immunology have allowed discovery of the biologically active components of CMH and the mechanisms of their anti-cancer activities. This chapter provides an overview of CMH use in treating cancer, including discussion of the anti-cancer mechanisms for individual herbs that are commonly used to treat cancer in contemporary TCM practice. Most CMH cancer research studies have involved in vitro and in vivo animal studies, with a relative paucity of well designed, placebo-controlled human clinical trials. Despite this, there is evidence that CMH may mitigate immunosuppression from conventional chemotherapy and radiotherapy, reduce side effects from those treatments, and improve cancer patients’ overall clinical status. Chinese medicinal herbs may produce tumour apoptosis, reduce metastases, and increase survival, either alone or in combination with conventional chemotherapy. Some CMHs interfere with conventional chemotherapy when administered simultaneously, yet enhance conventional chemotherapy efficacy when administered sequentially. Further controlled clinical trials of CMH with/without conventional chemotherapy and radiotherapy in cancer patients are needed to determine which herbs (and herb combinations) to use and the optimal timing of their administration to optimize cancer patients’ survival, reduce tumour burden, enhance immunologic function and improve quality of life while minimizing the side effects (e.g. nausea/vomiting, anorexia and fatigue) of conventional radiotherapy or chemotherapy.