Hydroxyapatite (HA) is a biomaterial with excellent biocompatibility. However, the brittleness and low fracture toughness of HA have limited its biomedical applications. As such, HA has been incorporated with zirconia (ZrO2) to enhance its mechanical strength. However, ZrO2 addition decreases the phase stability of HA. HA decomposition is not favored because it decreases the mechanical strength of HA/ZrO2. In this paper, the effect of sintering on HA decomposition is reviewed. Experimental results show that hot isostatic pressing of HA/ZrO2 is one of the most effective methods to suppress HA decomposition, yielding the highest relative density compared with other sintering methods.