The exploitation of photocatalysts that harvest solar spectrum as broad as possible remains a high‐priority target yet grand challenge. In this work, for the first time, metal–organic framework (MOF) composites are rationally fabricated to achieve broadband spectral response from UV to near‐infrared (NIR) region. In the core–shell structured upconversion nanoparticles (UCNPs)‐Pt@MOF/Au composites, the MOF is responsive to UV and a bit visible light, the plasmonic Au nanoparticles (NPs) accept visible light, whereas the UCNPs absorb NIR light to emit UV and visible light that are harvested by the MOF and Au once again. Moreover, the MOF not only facilitates the generation of “bare and clean” Au NPs on its surface and realizes the spatial separation for the Au and Pt NPs, but also provides necessary access for catalytic substrates/products to Pt active sites. As a result, the optimized composite exhibits excellent photocatalytic hydrogen production activity (280 µmol g−1 h−1) under simulated solar light, and the involved mechanism of photocatalytic H2 production under UV, visible, and NIR irradiation is elucidated. Reportedly, this is an extremely rare study on photocatalytic H2 production by light harvesting in all UV, visible, and NIR regions. Novel broadband spectrum‐responsive metal–organic framework (MOF) composites, upconversion nanoparticles‐Pt@MOF/Au, are fabricated based on plasmonic and upconversion effects. Strikingly, the composites exhibit considerable photocatalytic hydrogen production activities under UV, visible, or even near‐infrared light irradiation, which represents the first work reporting hydrogen production photocatalysts with considerable activity toward all these three regions of light irradiation.