The purpose of this research was to investigate the effects of Calendula officinalis extract (CE) on the activation of murine lymphocytes and macrophages. CE was administered p.o. once a day for 7 days at the concentration of 500 mg/kg. The administration of CE increased the viability of thymocytes, but decreased the viability of splenocytes. Also, CE increased the viability of thymocytes and splenocytes at the concentration of $5{mu}g$/ml in vitro. The administration of CE did not affect the population of thymic $CD4^+$/$CD8^+$ cells and splenic $CD4^+$/$CD8^+$ cells. Furthermore, the administration of CE enhanced the phagocytic activity of peritoneal macrophages, but decreased the phagocytic activity in vitro. CE decreased the production of nitric oxide from peritoneal macrophages in vivo and in vitro system. These results suggest that CE enhance of cell viability by a direct influence on thymocytes and phagocytic activity by an indirect influence on peritoneal macrophages.