<p>Bio-dicalcium phosphate (BDCP) is a natural source of calcium that can be extracted from biological sources such as catfish bones, a by-product of catfish. The huge amount of fish bone generated from the processing of catfish in Vietnam is a potential source for bio-calcium. The production of BDCP from this by-product can increase its value. Catfish bones collected from the factory were stewed and treated with NaOH solution to remove organic impurities. The pre-treated catfish bones were then calcined and ground to fine powder before converting to dicalcium phosphate. Important factors affecting the conversion including H₃PO₄ concentration, FBP concentration in H₃PO₄ solution, precipitation pH, reaction time, and reaction temperature were investigated. XRD, SEM, FTIR, and TGA were employed to characterize the BDCP products. BDCP with high purity was obtained at H₃PO₄ 3&#xa0;M, FBP concentration in H₃PO₄ of 80&#xa0;g&#xa0;L⁻¹, pH 5, reaction time 60&#xa0;min at 60&#xa0;°C. The product exhibited a notably high crystallinity (&gt; 96%) with particle sizes, ranging from 1 to 3&#xa0;μm, and crystal sizes of approximately 8&#xa0;nm. Elemental profiles analysis revealed that the product contains not only a high percentage of calcium and phosphorus but also other essential minerals. The process can be claimed as a viable method for acquiring premium-grade bio-calcium.</p> Graphical abstract <p></p>