Medicinal plants have been used for the treatment of several diseases since ancient times, but their anticancer properties have not been well studied. Herbal medicine has been used as a major treatment for cancer in various countries in South East Asia and the Middle East and Europe a long time ago. People looked for drugs in nature to retaliate diseases based on experience and there was not sufficient information either concerning the reasons for the illnesses or concerning which plant and how it could be utilized as a cure. Although many advanced countries have considered traditional herbal medicine as an official treatment for cancer, only 5-15% of these herbs have been investigated to detect their bioactive anticancer compounds. Several plant-derived compounds have shown promising anticancer therapeutics and attempts have been made to characterize the effectiveness of active constituents to be isolated from natural sources as chemo-preventive agents for rapid relief. H. mysorense (Hypericaceae) found at high elevation in the Western Ghats of India especially in Nilgiris. H. mysorense are mentioned in traditional system of folklore for its skin-related disorders, wound healing, spasmolytic, antipsychotic antifungal, and antiviral and nerve-calming properties. The present study was conducted to determine the anticancer activity of methanol leaf extract of H. mysorense on HT29 and A549 cells by MTT assay method. The maximum dead cells of HT29 were 59.67±0.73% and dead cells of A549 were 63.27±1.80 at 100 µg/mL concentration by leaf extract of H. mysorense.