Onion a very commonly used vegetable, ranks third in the world production of major vegetables. Apart from imparting a delicious taste and flavor due to its food in many Recipe preparations, it serves several medicinal purposes also. Processing and preservation of onion by suitable means is a major thrust area since a long time. The various kinds of treatments followed for dehydration of onion such as convective air drying, solar drying are reviewed here. These techniques are mainly used for preservation and value addition of onion.