The presence of chromium ion in drinking water has been proven to be toxic and carcinogenic. Hence, an attempt has been made to synthesize magnetic Fe₃O₄ fabricated with nano-hydroxyapatite (n-HAp)/gelatin (Gel) biocomposite by both in situ precipitation (in situ) and hydrothermal (hydro) methods. The hydrothermal-assisted Fe₃O₄@n-HApGel biocomposite achieved enhanced sorption capacity (SC) compare to the in situ precipitation method. The physico-chemical properties of the as-synthesized adsorbents were thoroughly characterized using various advanced instrumental techniques, namely, FTIR, XRD, SEM, EDAX, TEM and BET surface area analysis. Chromium adsorption mechanism of hydrothermal-assisted Fe₃O₄@n-HApGel composite was described by electrostatic attraction with surface complexation and reduction. The chromium adsorption behaviour of hydrothermal-assisted Fe₃O₄@n-HApGel biocomposite was interpreted using Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherms. The thermodynamic experimental data of Fe₃O₄@n-HApGel biocomposite indicates that the chromium sorption process is endothermic and spontaneous in nature. Fe₃O₄@n-HApGel composite can be easily recycled for more than 5 cycles using NaOH eluent. In addition, the magnetic biocomposite is also suitable for treating chromium polluted ground water.