Electroplating effluent contains many heavy metals including Zinc (Zn) and Nickel (Ni) are some of the crucial metals which exist in high concentrations. Calcium Oxide nanoparticles (CaONPs) and CaO/Fe2O3 nanocomposite (CaO/Fe2O3NC) were synthesized to evaluate the feasibility of Zn (II) and Ni (II) removal from wastewater. CaO NPs were successfully synthesized from waste eggshells by the sol–gel process while the chemical precipitation method was used for the synthesis of CaO NC. The morphology of the prepared material was characterized by X-ray diffraction (XRD), DLS, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) analysis. Batch studies were performed to assess the effect of pH, time, and adsorbent dose on the adsorption efficiency of the nanoparticle and nanocomposite for Zn (II) and Ni (II) removal. Inductively coupled plasma mass spectroscopy (ICP-MS) was used to monitor the amount of Zn (II) and Ni (II) ions in the aqueous solutions. The adsorption capacity of both metal ions increases with an increase in pH, with maximum adsorption occurring at pH 8. An optimum dose of 75 mg/L was observed with both CaO nanoparticle and CaO/Fe2O3 nanocomposite to remove Zn (II) and Ni (II) while equilibrium was achieved after 1 h. The high adsorption capacity makes these adsorbents a promising candidate for removal of metal ions from electroplating effluent.