The growing interest in improving Mg-based alloys’ corrosion properties stimulates the development of Mg-Y-Zn alloys with long-period stacking-ordered (LPSO) structures. In this work, to describe the corrosion performance of Mg-LPSO alloys, a set of experiments, including microstructure observations and corrosion testing in media containing various concentrations of chloride ions, were carried out. It was shown that the main corrosion mechanism occurring on the alloys was not only related to the volume of LPSO structures in the Mg matrix but was also dependent on their distribution. In the chloride-containing solutions, pitting was the predominant corrosion mechanism, and with the increasing chloride concentration, microgalvanic corrosion was accelerated.