Hydroxyapatite (HAp) [Ca10(PO4)6(OH)2] is a ceramic class of material widely used for medical applications. The HAp has been synthesized from Indonesian crab shells using a precipitation method at different temperatures synthesis ranging from room temperature to 80°C. The HAp was characterized using FTIR, XRD, SEM-EDS. The results demonstrate that the synthesis temperature of the HAp affected the functional groups, the phase, the crystal size, the crystallinity, the morphology, and the calcium to phosphorus ratio (Ca/P ratio). Synthesis at 80°C was identified as the optimal temperature synthesis to produce HAp from Indonesian crab shells as indicated by the crystalline pattern achieving the pure Hap by having the Ca/P ratio closest to theory (1.67), the morphology more uniform in size, and the complete of the HAp functional group.