Partial hydrogenation of benzene to cyclohexene is attractive in terms of feedstock accessibility, atomic economy, and operational simplicity. Herein, a series of Ru/ZrO2 catalysts were prepared by post-treatment of a binary Ru–Zn/ZrO2 catalyst using 5–30 wt % NaOH aqueous solutions. Alloying between Ru and Zn was evidenced for the catalyst post-treated only by water (Ru/ZrO2-0). Alkaline post-treatment removed metallic Zn, forming smaller Ru nanoparticles. Concomitantly, the hydrophilicity of the catalysts was increased and maximized on the 10 wt % NaOH-treated catalyst (Ru/ZrO2-10). In partial hydrogenation of benzene, the Ru/ZrO2-0 catalyst displayed the highest turnover frequency but the lowest initial selectivity to cyclohexene, whereas the Ru/ZrO2-10 catalyst exhibited the highest initial selectivity (86 %) and yield of cyclohexene (51 %) among the catalysts investigated. A quantitative relationship between the initial selectivity to cyclohexene and the hydrophilicity of these catalysts was identified, which rationalizes the significant impact of alkaline post-treatment on selectivity enhancement in partial hydrogenation of benzene to cyclohexene over Ru/ZrO2 catalysts.