<p>This study aims to fabricate a chitosan-based magnesium oxide nanohybrid for the adsorption-based remediation of toxic metals from contaminated water. Magnesium oxide nanoparticles were synthesized using <i>Duranta erecta</i> leaf extract followed by in situ polymerization-based fabrication of chitosan-integrated magnesium oxide nanohybrid. Various analytical techniques were employed to characterize the chemical and surface composition of the proposed materials. The acquired finding revealed the interaction between magnesium oxide and hydroxide or amine groups of chitosan in the fabricated magnesium oxide nanohybrid with its nanosized rough surface and less intense cubic crystalline structure than the parent magnesium oxide nanoparticle. The proposed material was quantitatively adsorbed Pb and Cd at pH 6 whilst Cr was absorbed at pH 7 based on the batch experiment followed by 50&#xa0;mg magnesium oxide nanohybrid dosage in 30&#xa0;min with 30&#xa0;mg L⁻¹ an initial concentration of toxic metals. Adsorption of the investigated TMs onto magnesium oxide nanohybrid occurs by multilayer development and pseudo-second-order kinetics in an endothermic and spontaneous condition. The quantitative adsorption capability of the suggested magnesium oxide nanohybrid allowed for the effective removal of toxic metals up to 97% with the adsorption capacities of 117, 116 and 118&#xa0;mg&#xa0;g⁻¹ for Cd, Pb, and Cr^VI, respectively. Magnesium oxide nanohybrid is a reusable adsorbent for up to 10 consecutive runs, resulting in a &lt; 5% drop in toxic metals adsorption. Furthermore, applying magnesium oxide nanohybrid to surface water samples resulted in the quantitative removal of toxic metals (&gt; 93%).</p>