Egg is the largest biological cell known which originates from one cell division and is composed of various important chemical substances that form the basis of life. The avian egg is an important source of nutrients, containing all of the proteins, lipids, vitamins, minerals and growth factors required by the developing embryo, as well as a number of defence factors to protect against bacterial and viral infection. This review mainly focuses on biological activities of proteins and peptides derived from egg components. Several biological activities have now been associated with egg components, including novel anti-microbial activities, anti-adhesive properties, immunomodulatory, anti-cancer, and anti-hypertensive activities, anti-oxidant properties, protease inhibitors, nutrient bioavailability and functional lipids, highlighting the importance of egg and egg components in human health, and disease prevention and treatment.