The Siddha and Unani systems of medicine, like Ayurveda, rely heavily on herbal plants for treating various diseases. Phytochemical analysis plays a crucial role in understanding the bioactive compounds responsible for the therapeutic effects of these plants. This study investigates the phytochemical constituents of selected medicinal plants used in Siddha and Unani medicine, such as Kalmegh (Andrographis paniculata), Amla (Phyllanthus emblica), and Haritaki (Terminalia chebula). Using advanced analytical techniques, the research identifies and quantifies bioactive compounds, including terpenoids, phenolic compounds, and glycosides. The study demonstrates the significance of phytochemical diversity in the medicinal efficacy of these plants and suggests further research for developing standardized herbal formulations.