Antioxidants are the agents that prevent the oxidation of molecules in the metabolism of living things. Generally, antioxidants play an essential role in inhibiting oxidation by the release mechanism of a singlet oxygen atom, and that oxygen atom can neutralize another nascent oxygen atom because the nascent oxygen can form free radicals. These free radicals are a chain-like reaction; they can collapse the proper metabolic activity. Hence, the antioxidants are essential to regulate the metabolism. These antioxidants are broadly divided into two groups based on their sources. One is natural and another one is synthetic. The natural antioxidants fall into specific subdivisions based on their nature of origin. Some vitamins act as antioxidants, like vitamins A, B-complex, C, D, and E. Minerals act as antioxidants, such as selenium, copper, iron, and zinc. Flavonoids, phenols, and tannin-like phytochemicals are also examples of antioxidants. This chapter reviewed how antioxidants act as a food, fodder, and cosmetics preserving agent. Antioxidants restrict oxidation and eradicate the free radical formation in living things; hence, they can preserve biologically based things and oxidize foods and oxidizable things. In the food industries, some vitamins and selenium-like minerals are used as preserving agents to resist free radical formation and maintain their physiological characteristics. In animal food, antioxidants, including vitamin E and polyphenols, are used as preservatives for fodder. In cosmetics, polyphenols, vitamins, and selenium play an antioxidative role. The antioxidants are nontoxic and essential to living things to maintain metabolism and the quality of the products. In some cases, these antioxidants are also used as packing material for food products. Hence, antioxidants are irreplaceable for preserving food, fodder, and cosmetics.