Sweet flag (Acorus calamus) is mentioned in Ayurveda and belongs to the genus Acorus L. of the family Acoraceae and is widely distributed temperate to sub temperate regions. It is commonly used in traditional medicinal systems of Asian and European countries to treat appetite loss, diarrhoea, digestive disorders, bronchitis indigestion, chest pain, nervous disorders. This review focuses on the therapeutic potential of essential oils, phenyl propanoids, sesquiterpenes and monoterpenes as well as xanthone, glycosides, flavones, lignans, steroids and inorganic constituents.