<p>Bacterial infections continue to pose a significant global health challenge. As a result, there has been a growing effort to develop antibacterial agents. Among these agents, nanocomposites, particularly bio-nanocomposite, have been found to demonstrate promising potential in combating bacterial resistance. In this context, a Fe₃O₄-HAp@Mg-GA bio-nanocomposite was synthesized <i>via</i> an in-situ process that incorporates magnesium-gallic acid metal-organic framework (Mg-GA MOF) and magnetic hydroxyapatite (Fe₃O₄-HAp). Advanced analytical techniques, including ATR, XRD, VSM, SEM, EDX, and zeta potential analysis, were employed to characterize the synthesized material. The release profiles of gallic acid (GA) and magnesium (Mg) ions were evaluated in a simulated physiological environment (PBS, pH 7.4), showing a controlled release over 72&#xa0;h. Surface modification of Fe₃O₄-HAp with Mg-GA MOF notably enhanced its antibacterial properties. Antibacterial assays demonstrated significant inhibitory effects against both gram-positive (<i>Staphylococcus aureus</i>) and gram-negative (<i>Escherichia coli</i>) bacteria, with a minimum inhibitory concentration (MIC) of 1.5&#xa0;mg/mL. Biocompatibility was confirmed using MTT assays, revealing that the bio-nanocomposite maintained over 75% cell viability in human dermal fibroblast cells (HFF-2) after 48&#xa0;h of treatment. These findings highlight the potential of Fe₃O₄-HAp@Mg-GA as a promising antibacterial material for biomedical applications, offering effective bacterial inhibition combined with biocompatibility.</p>