The need for biomaterials in dental and orthopedic applications has increased as the world population ages. Synthetic calcium phosphate bioceramics and calcium phosphate cements are proved potential substitutes for bone and teeth due to their structural and crystallographic similarities with the biological apatites, and their biocompatibility but they show poor mechanical properties. Chlorapatite and hydroxyapatite whiskers with high aspect ratio can be used to improve this drawback. This work describes a method to transform chlorapatite single crystals into hydroxyapatite whiskers, suitable for the reinforcement of calcium phosphate bioceramics and calcium phosphate cements. Hydroxyapatite whiskers were obtained by treating chlorapatite single crystals in high-temperature hydrothermal conditions. The variable studied was furnace temperature with and without moisture conditions. The characterization of the chlorapatite and hydroxyapatite whiskers was carried out by SEM, XRD, EDS and FTIR. SXRD data were analyzed for the description of the chlorapatite structure.