Herpes simplex viruses (HSV-1 and -2) are important pathogens for humans, especially in the case of highly susceptible adults. Moreover, HSV-2 has been reported to be a high risk factor for HIV infection. Therefore, the discovery of novel anti-HSV drugs deserves great efforts. In this paper, we review anti-HSV substances from natural sources, including both extracts and pure compounds from herbal medicines, reported in studies from several laboratories. The role of traditional medicine for the development of anti-HSV compounds is also discussed. Interestingly, it was found that traditional medicines, like Ayurvedic, traditional Chinese (TCM), Chakma medicines, are good and potential sources for promising anti-HSV drugs. A second objective of this review is to discuss several anti-HSV compounds with respect to their structure-activity relationship (SAR). A large number of small molecules, like phenolics, polyphenols, terpenes (e.g., mono-, di-, tri-), flavonoids, sugar-containing compounds, were found to be promising anti-herpetic agents. Our major conclusion is that natural products from medicinal plant extracts are very important source of anti-HSV agents.