In this work, sol–gel dip coating technique was used to coat magnesium/hydroxyapatite (Mg/HA) slurry with incorporating 10 and 30% of epoxy as binder on high carbon Co–Cr–Mo medium-entropy alloy (MEA). High carbon Co–Cr–Mo MEA which priory have been treated via thermal oxidation at 850 and 1050 ℃ for 2 h under controlled furnace atmosphere which to create an oxide layer for surface modification purposes. The coating of Mg/HA on oxidized substrate were then investigated by using Field Emission Scanning Electron Microscopy (FESEM) with Energy Dispersive X-ray spectroscopy (EDX) and X-ray Diffraction (XRD) to evaluate the optimum substrate surface condition for further investigation. Findings from this study revealed that oxidation at 1050 ℃ on high carbon Co–Cr–Mo MEA demonstrates good anchorage for Mg/HA coating layer to adhere on the substrate surface and the presence of magnesium cobalt oxide indicate that substrate surface advantageous to act as antifungal agent to human body. Furthermore, by incorporating 30% of epoxy to Mg/HA slurry has improved the coating morphology. The results showed absent of microcracks and high microporous of Mg/HA with dominating sizes range from 27.9 to 188.5 µm which is believed can promote greater biocompatibility on high carbon Co–Cr–Mo MEA.