Due to the remarkable chemical, electrical, and optical properties, calcium oxide (CaO) is an incredibly significant industrial substance that is utilized as a paint additive, catalyst, toxic-waste treatment agent, and for other basic uses. CaO exhibit cubic structure and can be grown using various chemical and physical methods. The different ways to create CaO nanoparticles from biological materials, such as papaya, green tea, red dragon fruit, and Moringa oleifera plant leaves, are highlighted in this review along with some additional techniques such as sol-gel, solution combustion, precipitation, and microwave irradiation methods. CaO nanoparticles are an excellent alternative in polymer nanocomposites as antimicrobial filler to be applied for food packaging or medical devices. Also, they show their effective utilization in various disciplines such as agriculture, biomedical and environment. Application of CaO nanoparticles in these fields are also included in concise and concrete way.