Nowadays, plant-based chemicals have drawn the attention of pharmacy researchers due to their potent biological activity against various ailments. In this series, terpenes and terpenoids are gaining popularity among drug researchers gradually. Terpenes are naturally occurring large and varied class of hydrocarbons substances produced by a wide variety of plants including fruits, vegetables, flowers and some animals. Their concentration is generally high in plants. A broad range of the biological properties of terpenoids includes cancer chemo-preventive effects, antimicrobial, antifungal, antiviral, anti-hyperglycemic, anti-inflammatory, anti-parasitic activities and memory enhancers. Terpenoids are usually cyclic unsaturated hydrocarbons, with the altered number of oxygen moieties in the constituent groups attached to the basic isoprene skeleton. Terpenoids are a group of substances that occur in nearly every natural food. Terpenoids display a wide range of biological activities against cancer, malaria, inflammation, tuberculosis and a variety of infectious diseases including viral as well as bacterial. In this chapter, we have emphasized the proven and expected medicinal value of both terpenes and terpenoids.