A triazine-based dendrimer-coated magnetic nanomaterial (Fe3O4@SiO2@D-G3) was successfully synthesized. The structure and composition of the synthesized catalyst were characterized by FT-IR, XRD, EDX, SEM, TEM, TGA, and VSM techniques. Structural characterization of the newly synthesized adsorbent confirmed the modification of magnetic nanoparticles by dendrimer molecules. The adsorption performance of this novel dendritic nanomaterial was evaluated for the removal of heavy metal contaminants with sustainability concerns. The effect of essential parameters, including pH, initial metal ion concentration, adsorbent dosage, and contact time was investigated. The prepared adsorbent showed good binding ability with Pb(II) and Cd(II) metal ions and excellent adsorption efficiency toward these contaminants from aqueous media (93.6%, 98.5%). The heavy metal ions could be adsorbed by coordination to the hydroxyl and amine functional groups of ethanolamine moiety and also triazine amine groups and electrostatic interactions. The adsorption process with Pb(II) and Cd(II) metal ions was exothermic and fitted perfectly with the Freundlich isotherm with a high correlation coefficient (R2 = 0.9739, 0.9069) and adsorption capacity (24.317, 84.68 mg g-1 ) and pseudo-second-order kinetic model. Recycled hybrid nanomaterial was dried and applied to different adsorption–desorption tests and desorption efficiency was found to be 98%. The results provide new insights into the applications of dendrimer-decorated magnetic nanoparticles in the fast removal of heavy metal ions.