Magnesium (Mg) alloys, a novel class of degradable, metallic biomaterials, have attracted growing interest as a promising alternative for medical implant and device applications due to their advantageous mechanical and biological properties. Although its biodegradability is an attractive property, rapid degradation of Mg in the physiological environments imposes a major obstacle that limits the translation of Mg-based implants to clinical applications. Therefore, the objective of this study was to develop a nanostructured hydroxyapatite (nHA) coating on polished Mg substrates to mediate the rapid degradation of Mg while improving its integration with bone tissue for orthopedic applications. The nHA coatings were deposited on polished Mg using the patented transonic particle acceleration (Spire Biomedical) process. Surface morphology, elemental compositions, and crystal structures were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction (XRD) analysis, respectively. The degradation of nHA-coated and non-coated Mg samples was investigated by incubating the samples in phosphate buffered saline and revised simulated body fluid, under standard cell culture conditions. Rat bone marrow stromal cells (BMSCs) were harvested and cultured with nHA-coated and non-coated Mg samples to determine cytocompatibility. The degradation results suggested that the nHA coatings decreased Mg degradation. Improved BMSC adhesion was observed on the surfaces of the nHA-coated and non-coated Mg samples, in comparison with the cells on the culture plate surrounding the Mg samples. In conclusion, nHA coatings showed promise for improving the biodegradation and cytocompatibility properties of Mg-based orthopedic implants and should be further studied. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.