A facile and efficient γ-radiation strategy has been developed to incorporate surface-clean metal nanoparticles (NPs) into UiO-66-NH₂ in the absence of stabilizing agents and additional reductants. This approach is enabled by metal ion reduction with active e⁻_aq and H˙ species derived from water radiolysis. As a result, highly dispersed Pd NPs with narrow size distribution were generated and evenly dispersed in UiO-66-NH₂. More importantly, the radiation-reduced Pd NPs exhibit significantly enhanced catalytic activity and stability in olefin hydrogenation. Meanwhile, they are also highly active in the catalytic reduction of 4-nitrophenol to 4-aminophenol. Furthermore, the proposed radiation methodology could be successfully extended to prepare other metal NPs such as Au and Pt. Considering that γ-ray radiation is widely used in industry, this study provides a potentially scalable approach to incorporate metallic nanomaterials into metal–organic frameworks with improved catalytic performance.