Removal of Pb(II) ions from aqueous solutions using modified-NiO nanoparticles (m-NONPs) prepared through chemical reaction of NiO nanoparticles (NONPs) with 3-aminopropyltriethoxysilane was investigated in a batch system. The influence of experimental conditions including contact time, pH, Pb(II) concentration and presence of diverse ions on Pb(II) adsorption was studied. The results indicated that the adsorption process correlated with the Langmuir and Freundlich models. Themaximumadsorption capacity ofm-NONPswas found to be 100.2 mg g-1 which is considerably more than that of NONPs. The results suggest thatm-NONPs is potentially efficient for removing Pb(II) ions fromaqueous solutions.