Dimensionality plays a vital role at the nanoscale in tuning the electronical and photophysical properties and surface features of perovskite nanocrystals. Here, 3D and 1D all-inorganic CsPbBr3 nanocrystals were chosen as model materials to systemically reveal the dimensionality-dependent effect in photocatalytic H2 evolution. In terms of facilitating photoinduced electron-hole pair separation and charge transfer, as well as inducing proton reduction potential with the presence of fewer Br vacancies, 1D CsPbBr3 nanorods gave about a 5-fold improvement for solar H2 evolution.