This work investigates the effect of varied sintering temperatures on the structural, physical, and mechanical properties of activated-hydroxyapatite (HAp) ceramic, with a focus on its potential implications for biomedical applications. Activated metakaolin (MK)/HAp specimens were prepared using an alkaline activation technique, maintaining a fixed metakaolin loading in HAp at a liquid-to-solid (L/S) ratio of 1.25. These specimens were subjected to pressing and sintering across a temperature range of 800 °C to 1200 °C. Results were comprehensively analysed through phase analysis, thermal analysis, surface morphology study, and evaluations of mechanical and physical properties. Phase analysis revealed the formation of multiple crystalline phases within the sintering temperature range of 800 °C to 1100 °C, while sintering at 900 °C resulted in the formation of a single monoclinic hydroxyapatite phase, providing the highest recorded tensile strength of 12.52 MPa. X-ray diffraction (XRD) results also indicated the presence of a semi-crystalline phase at 1200 °C, consistent with crystallization peak temperatures (Tp) of 1070 °C observed in thermal analysis. In conclusion, this study underscores the significant influence of sintering temperature on the phase stability and overall properties of activated-HAp ceramic, with sintering at 900 °C facilitating the formation of a single monoclinic hydroxyapatite phase. Additionally, the observed low-fusion phenomenon at 1200 °C presents intriguing possibilities for broader biomedical applications.