Ginsenoside Rg3 (Rg3) is one of the most effective steroidal saponins extracted from Ginseng, a common Traditional Chinese medicine (TCM) herb which tonifies Qi in TCM theory and inhibits tumors. Rg3 suppresses tumor growth and tumor angiogenesis. For its significant antitumor effects, Rg3 has been used in clinical trials in combination with chemotherapy regimens. 20(S) and 20(R) forms of ginsenosides are stereoisomers of each other that depend on the orientation of the C-20 hydroxyl in ginsenosides. In general, the 20(S) compounds have been shown to possess better anti-proliferative effects than their 20(R) counterparts whereas 20(R) compounds such as 20(R)-Rg3 have been shown to inhibit cancer cell invasion and metastasis. Ginsenoside Rg3 regulates voltage-gated ion channels such as Ca(2+), K(+), and Na(+) channels, and ligand-gated ion channels such as GABAA, 5-HT3, nicotinic acetylcholine, and N-methyl-D-aspartate (NMDA) receptors through interactions with various sites including channel blocker binding sites, toxin-binding sites, channel gating regions, and allosteric channel regulator binding sites when the respective ion channels or receptors are stimulated with depolarization or ligand treatment. Shenyi capsule which contains ginsenoside Rg3 as the main ingredient has been approved by China Food and Drug Administration (CFDA) to be used clinically for cancer treatment.