The electron localizability indicator—an efficient quantum chemical tool for analysis of chemical bonding—is applied to unveil the chemical bonding behind the CO adsorption on the (̅1̅1̅1) surface of the highly selective semi-hydrogenation catalyst GaPd. Refining the commonly applied Blyholder model, the obtained results are in excellent agreement with previous experimental and theoretical findings. The clean GaPd(̅1̅1̅1) surface presents unshielded negatively charged Pd centers and positively charged Ga species partially shielded by dangling bonds. The CO molecule adsorbs on-top of the Pd centers perperdicular to the surface, while no CO-Ga interaction is observed. The chemical bonding analysis results in deep understanding, thus enabling a cost efficient route to innovative materials by reverse engineering.