The use of magnesium and its alloys for bone implants, cardiovascular stents, and wound closing devices have received considerable attention recently, however, their rapid degradation remains a major concern. Mg-based alloys degrade in the body prior to the completion of their specified healing period. Various biocompatible coatings have been used to overcome this shortcoming and to improve the surface properties such as hardness, corrosion resistance, and biocompatibility. The biocompatible materials used include calcium phosphate (Ca-P), hydroxyapatite (HA), octa calcium phosphate (Octa-Ca-P), metals (Zr, N, Hf, Nd, Zn, Cr, O, Ti), metal oxides (Al2O3, ZrO2, Cr2O3, SiO2, TiO2, Ta2O5, MgO), fluorides, and biopolymers. This paper reviews the surface treatment techniques utilized for Mg and Mg alloys. Additionally, related problems and possible solutions for Mg-based alloys with cytotoxicity are discussed.