In Traditional Chinese Medicine (TCM), ginseng roots are taken orally as a pharmacological adaptogen and nourishing stimulants for thousands of years. Along with the rapid advancement of modern life technologies, ginseng's effects as a non-toxic non-organ-specific cancer preventive agent have recently been elucidated both at molecular levels and on clinical aspects. Here we presented some techniques used for separating ginseng active ingredients, evidence of effects of ginseng and its ingredients on cancer and cancer metastasis obtained from in vitro and in vivo experiments and thousands of volunteers participated in various clinical trials. As a biological response modifier and an adaptogen to synergistically enhance efficacy of conventional therapy as a supplement, adequate ginseng consumption reduces the risk of development of all types of cancer and the recurrence of some types of cancer, improves host intrinsic response to cancer and quality of patients' life. We also briefly stated recent case reports on potential interaction between warfarin and ginseng products.