The use of implants for bone repair has a considerable and successful history. Traditionally, metallic implants have been used in such a way that the implant would be surgically removed after sufficient bone healing has been achieved. During the last decade, interest in biodegradable magnesium (Mg) implants has increased dramatically. The use of Mg is based on the fact that Mg is one of the essential elements for human metabolism, and the density and elastic modulus of Mg are close to the human bone, thus, avoiding stress shielding effect. However, Mg alloys corrodes too rapidly, resulting in hydrogen evolution and consequently, local alkalization close to the surgery region as well as premature degradation in the implant's mechanical integrity before bone healing occurred. All these factors impede the practical applications of Mg implants. In this study, a hydrothermal coating process was used to provide, uniform and biodegradable inorganic calcium-phosphate (Ca-P) and calcium-phosphate/polymer (Ca-P/Polymer) composite coatings on AZ31 magnesium substrate that slow the corrosion of Mg and to meet different requirements for implant application. In the current study two different types of novel Ca-P/Polymer composites coatings were successfully deposited for the first time on AZ31 magnesium alloy to reduce CaP material brittleness by using polyacrylic acid and carboxymethyl cellulose polymers. The results showed, crystal phase and coating's morphology could be successfully controlled by the type and concentration of polymer used which could affect the coating's degradation rate as well. Incorporation of polymer in the CaP coatings reduced the coating elastic modulus bringing it close to that of Mg and that of human bone. Apart from mechanical properties, cell proliferation studies indicated that composite coatings induced better cell attachment compared to the purely inorganic CaP coating.