<p>This study investigates, for the first time, the effect of cryogenic rolling on the microstructure and mechanical behavior of Mg–Zn–Y alloys containing long-period stacking-ordered (LPSO) phases. Two compositions, Mg₉₇Zn₁Y₂ and Mg₉₅Zn₂Y₃ (at.%), were processed by cryogenic rolling after a previous hot rolling step. Scanning electron microscopy revealed significant fragmentation of the LPSO phases, with particles smaller than 1&#xa0;µm homogeneously distributed within the matrix. X-ray diffraction analysis using the Williamson–Hall method showed an increase in microstrains, indicating a higher crystal defect density induced by cryogenic deformation. These microstructural changes resulted in notable improvements in hardness, with Vickers microhardness increasing by 16.8% in the Mg₉₇Zn₁Y₂ alloy and by 14.5% in Mg₉₅Zn₂Y₃, compared to their respective hot-rolled states. The enhancement in mechanical properties is attributed to the fragmentation and homogeneous distribution of the LPSO phase particles, which act as effective barriers to dislocation motion, thus contributing to an increase in defect density. Importantly, no precipitation of secondary phases was detected, confirming the stability of the LPSO phases during cryogenic processing. These results demonstrate that cryogenic rolling represents a promising processing route for strengthening Mg–Zn–Y alloys with LPSO structures.</p>