The immune system is known to be involved in the etiology as well as pathophysiological mechanisms of several diseases. Indian system of traditional medicines gives emphasis on promotion of health -a concept of strengthening host defenses against different diseases. The concept of immunomodulation relates to nonspecific activation of the function and efficiency of macrophages, granulocytes, complement, natural killer cells and lymphocytes and also to the production of various effector molecules generated by activated cells. Immunomodulators are substances that help to regulate the immune system. The basic mechanisms by which the herbs (active principle) defend the body against infection have two probable ways one by destroying pathogens and other by enhancing the body immunity. Siddha formulations beings a multi-componential formulation offers greater relief by strengthening the host defense mechanism by its versatile pharmacological action. Macrophage cell line RAW 264.7 is widely utilized themodel for evaluating the In vitro immunomodulatory efficacy of the several Siddha formulations. Naga Chendurum(NC) is one such novel Siddha formulation comprised of a combination of herbs including Baptisia bracfeata, Eclipta prostrata,Madhuga longifolia and minerals such as zinc, sulphur, red orpiment etc.The present study was carried out to evaluate the immunomodulatory activity of Siddha formulation NC using Macrophage cell line RAW 264.7 using lipopolysaccharide (LPS) (1µg/mL) as a control. LPS induced nitrite production used an indicator for evaluating the level of phagocytosis. The concentration was measured using the spectrophotometric technique at 540nm. The result obtained from the present investigation indicates that the drug NC exhibit a significant decrease in the level of nitrites in the cell line medium from 952.38 µg to 483.61 µg. The results clearly indicate that the formulation NC possess immune boosting properties and suggest a usefulness in the disorder of immunological origin where the antioxidant system is adversely affected.