Pd nanoparticles with a mean diameter of 2.2 nm on amine-functionalized UiO-66 were synthesized by facile anionic-exchange followed by chemical reduction. The prepared Pd/NH2-UiO-66 catalyst was effective in the catalytic transfer hydrogenation of nitrobenzene to aniline using formic acid as a hydrogen source under mild reaction conditions in water with a maximum nitrobenzene conversion of 98% and an aniline selectivity of 99%. The superior catalytic activity of Pd/NH2-UiO-66 was attributed to the cooperative effects of nano-sized Pd and its stabilization offered by the NH2-UiO-66 support. The heterogeneous nature of the catalytic system was confirmed by a hot-filtering test and the catalyst maintained stable performance in 4 repeated cycles. A plausible reaction mechanism was proposed.