The sorption properties of zirconium and hafnium toward a commercial macroporous anion exchanger (Amberjet 4200 Cl) in acidic chloride solutions were investigated. Variations of the distribution ratio, as a function of HCl concentration in the range of 0.1-12 M, were studied. Separation factors up to 9, under equilibrium conditions, were obtained with an HCl concentration of 9.5 M. Equilibrium isotherms of the binary system under those conditions were analyzed by Langmuir, Freundlich, Sips, and ideal adsorbed solution theory (IAST) adsorption models, using parameters obtained from single-component isotherms. For zirconium, the experimental data of a single isotherm were determined to follow Langmuir, Freundlich, and Sips models, whereas for hafnium, the single-component isotherm is well-described only by Freundlich and Sips equations. The maximum adsorption capacity obtained from the Langmuir isotherm was 0.94 mmol/g (86 mg/g) for zirconium. With regard to hafnium, it is not possible to estimate the adsorption capacity and the energy of adsorption separately from the experimental data. The predictions of binary adsorption isotherm of the zirconium-hafnium system showed good agreement with the experimental data when IAST was used with the Sips equation, except for hafnium at low concentration. The poor prediction for hafnium at low metal concentrations could be explained by the extrapolation of the single-solute isotherm equations in the region of very low concentration, where the models are linear.