Demineralized whey has good sensory and functional properties. As a result, it is important on the global market of food ingredients. Demineralized whey is part of numerous formulations, including baby food. As healthy diets and functional foods get more popular, the overall consumption of dairy products continues to grow. New whey processing technologies open greater opportunities for products with increased value. The review features modern industrial methods of whey demineralization, i.e., nanofiltration, electrodialysis, and ion exchange, as well as their advantages and disadvantages. Nanofiltration has low selectivity for monovalent ions, which means it provides only partial demineralization and concentration. Electrodialysis is an electromembrane process that separates ions from a solution with the help of electric field. It is more effective in removing minerals and provides 90% demineralization. However, its efficiency depends on the type of ions, their concentration, and membrane properties. High concentrations of divalent ions slow demineralization down and increase the processing time. The ion exchange method involves exchange resins, i.e., polymeric materials with functional groups that can bind to ions (cations or anions) in the solution and exchange ions. Different whey demineralization methods can be combined based on the type of raw materials and final product.