Hydroxyapatite (HA) ceramics derived from tuna bone (THA) was prepared and their mechanical property was investigated with immersion in buffered water. Tuna bones were soaked in 0.1 M of NaOH solution at 80°C for 1 h. After soaking, the bones were calcined at 800°C for 1 h to completely remove organic, and then attritor-milled for 24 h. The powders obtained were cold isostatically pressed and sintered at 1300°C with a dwell time of 1 h. Sintered densities of the THA was about 93%. After polishing, the THA were immersed in buffered water at 37 °C for 3 and 7 days. The THA ceramics consisted of HA and small amount of magnesium oxide. Immersion test revealed that there was no clear evidence of dissolution for the THA which sintered at high temperatures. Vickers hardness test showed that the hardness value of THA ceramics was not changed with immersion time indicating that dense hydroxyapatite from tuna bone was stable in liquid environment.