Plasma electrolytic oxidation (PEO) coatings are known for their excellent wear and corrosion resistance, but they often develop pores and microcracks during the arc discharge process, which compromise their long-term durability. Therefore, effective sealing treatments are critical to enhancing their performance. This chapter discusses recent advancements in posttreatment sealing strategies for PEO coatings, focusing on three main approaches: physical methods to improve surface properties, chemical sealing techniques that modify the coating’s chemical structure, and hybrid methods that combine both physical and chemical processes. These posttreatment strategies aim to enhance the adhesion, appearance, and overall functionality of PEO coatings. The chapter highlights sealing techniques that address the inherent limitations of PEO coatings, ultimately improving their quality and longevity.