Dairy industry is considered as an important food industry that provides various kinds of nutritionally rich dairy products for all age groups. Beside these nutritive values, dairy industry is contemplated as a good source of raw materials for other industries. Most importantly, dairy industry employs environment-friendly and energy-saving technologies. Membrane separation technology being one of those also focused on a cost-effective and environment-friendly manner, which can be widely applied in dairy industry for many useful purposes. In this chapter, we first define and classify the membrane separation technology and then comprehensively describe its applications, for instance, component separation, filtration, removal of bacteria, and wastewater treatment in dairy industry.