This paper presents a comprehensive synthesis method for nanohydroxyapatite (nHA) utilizing squid shell (cuttlefish) as a calcium source. The process involves sequential reactions starting with the calcination of calcium carbonate precursor obtained from squid shell to produce calcium oxide (CaO). Subsequent reactions with nitric acid and phosphate yield calcium nitrate Ca(NOâ) and phosphorous acid (HâPOâ), respectively, laying the groundwork for nHA synthesis. The controlled precipitation reaction of these solutions under specific pH and temperature conditions results in the formation of high-quality nHA particles. Characterization of the synthesized nHA using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR) confirms its structure, morphology, and composition. This synthesis approach offers a sustainable and cost-effective strategy for producing valuable biomaterials with potential applications in biomedical fields, showcasing the versatility and efficacy of utilizing seafood waste for biomedical material synthesis. © 2025 Elsevier B.V., All rights reserved.