Metal oxides and their composites have been extensively studied as effective adsorbents for the removal of heavy metals from aqueous solutions in environmental remediation. In this work, Cu_0.5Mg_0.5Fe₂O₄ was synthesized by a co-precipitation method followed by calcination (900 °C) and investigated for Pb(II) adsorption. The resultant samples were characterized by various analytical techniques including X-ray diffraction, N₂ adsorption–desorption, scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The results revealed that single-phase cubic spinel was obtained by the calcination of as-synthesized samples at a temperature of 900 °C. Cu_0.5Mg_0.5Fe₂O₄ ferrite is a mesoporous material with a surface area, a total pore volume, and an average pore size of 41.3 m²/g, 0.2 cm³/g, and 15.1 nm, respectively. Pb(II) adsorption on Cu_0.5Mg_0.5Fe₂O₄ fitted well to the Langmuir model, indicating monolayer adsorption with a maximum capacity of 57.7 mg/g. The pseudo-second-order kinetic model can exactly describe Pb(II) adsorption with the normalized standard deviation (Δq) of 1.24%. The obtained results confirmed that the Cu_0.5Mg_0.5Fe₂O₄ ternary oxides exhibit a high adsorption capacity toward Pb(II), thanks to the increase in active adsorptive sites of ferrite.