AbstractMagnesium alloys such as Mg–Ca and Mg–Zn–Ca are good orthopaedic materials; however their tendency to corrode is high. Herein we utilize selective laser melting (SLM) to modify the surface of these Mg alloys to simultaneously improve the corrosion behaviour and microhardness. The corrosion rate decreased from 2.1 ± 0.2 mm/y to 1.0 ± 0.1 mm/y for the laser-processed Mg–0.6Ca, and from 1.6 ± 0.1 mm/y to 0.7 ± 0.2 mm/y for laser-processed Mg–0.5Zn–0.3Ca. The microhardness increased from 46 ± 1 HV to 56 ± 1 HV for Mg–0.6Ca, and from 47 ± 3 HV to 55 ± 3 HV for Mg–0.5Zn–0.3Ca. In addition, good biocompatibility remained in the laser processed Mg alloys. The improved properties are attributed to laser-induced grain refinement, confined impurity elements, residual stress, and modified surface chemistry. The results demonstrated the potential of SLM as a surface engineering approach for developing advanced biomedical Mg alloys.