Deep cryogenic treatment has shown promise as a facile method of increasing the characteristics of many materials including alloys of iron, aluminum, and magnesium. However, there have not been any prior studies on its effect on the microstructure and thermal and mechanical properties of magnesium-based nanocomposites. In this study, a Mg/2wt.%CeO2 nanocomposite was processed using disintegrated melt deposition processing coupled with hot extrusion, followed by cryogenic treatment in liquid nitrogen for 24 h. The characterization results show increases in density (reduction in porosity), ignition temperature, compressive yield strength, compressive ductility, and microhardness. This study, for the first time, shows the significant relevance of deep cryogenic treatment in enhancing an array of properties of a magnesium-based nanocomposite that may be catalytic in improving its application spectrum.