Publisher Summary This chapter provides an overview of the imprinting polymerization for the recognition and separation of metal ions. One of the promising approaches to create molecular-recognizing materials is the molecular imprinting method. The technique of molecular imprinting consists of the following three steps: (1) synthesis of functional vinyl monomers that can interact with a target template, (2) free radical polymerization of the vinyl monomers with cross-linking reagents in the presence of the template, and (3) removal of the template from the cross-linked copolymer resin. Metal-ion imprinted resins can achieve the separation, recovery, and purification of valuable metal ions in a variety of matrices readily and efficiently. However, there may be some fundamental drawbacks, for example, complexation between imprint molecules and functional monomers is not always fast and water-soluble substances cannot be employed as imprint molecules. Thus, imprinting polymerization will be a promising way to recognize and separate metal ions, together with organic ions like amino acids and proteins.