Overly fast corrosion degradation of biodegradable magnesium alloys has been a major problem over the last several years. The development of protective coatings by using biocompatible, biodegradable, and non-toxic material such as chitosan ensures a reduction in the rate of corrosion of Mg alloys in simulated body fluids. In this study, chitosan/TiO₂ nanocomposite coating was used for the first time to hinder the corrosion rate of Mg19Zn1Ca alloy in Hank's solution. The main goal of this research is to investigate and explain the corrosion degradation mechanism of Mg19Zn1Ca alloy coated by nanocomposite chitosan-based coating. The chemical composition, structural analyses, and corrosion tests were used to evaluate the protective properties of the chitosan/TiO₂ coating deposited on the Mg19Zn1Ca substrate. The chitosan/TiO₂ coating slows down the corrosion rate of the magnesium alloy by more than threefold (3.6 times). The interaction of TiO₂ (NPs) with the hydroxy and amine groups present in the chitosan molecule cause their uniform distribution in the chitosan matrix. The chitosan/TiO₂ coating limits the contact of the substrate with Hank's solution.