Abstract This article is focused on the study of cooling rate effects on the thermal, structural, and microstructural properties of hydroxyapatite (HAp) obtained from bovine bone. A three‐step process was used to obtain BIO‐HAp: hydrothermal, calcinations, and cooling. Calcined samples in a furnace and cooling in air (HAp‐CAir), water (HAp‐CW), and liquid nitrogen (HAp‐CN2), as well as an air cooled sample inside the furnace (HAp‐CFAir), were studied. According to this study, the low cooling rate that was achieved for air cooled samples inside the furnace produce single crystal BIO‐HAp with better crystalline quality; other samples exhibited polycrystalline structures forming micron and submicron grains. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 339–344, 2016.