The development of 100% lead-free perovskite materials for photoelectrochemical applications is a hot topic in the current research scenario. Herein, by varying the preparation strategy, we have synthesized two distinct lead-free manganese halide perovskite nanocrystals (NCs), CsMnCl3(H2O)2 (1D-CMC3H) and Cs2MnCl4(H2O)2 (0D-C2MC4H), by simple ultrasonication/crystallization and a modified ligand-assisted reprecipitation (LARP) approach (room temperature synthesis), respectively. For the first time, a polar solvent methanol was used instead of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) for the synthesis of perovskite NCs. These two manganese halide perovskites exhibit unique morphology-dependent photoluminescence properties. The photoelectrochemical properties of these two Mn-halide-based perovskite NCs were evaluated through electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). The as-prepared one-dimensional (1D) and zero-dimensional (0D) Mn-halide perovskites exhibit more effectual dissociation of photogenerated electron–hole pairs as well as the presence of more rapid interfacial charge transfer on the photoelectrodes under light irradiation. Further improvement in the photoelectrochemical behavior of the 1D-CMC3H and 0D-C2MC4H perovskite photoelectrodes is achieved with eco-friendly ZnO. The overall photoelectrochemical performances of Mn-halide perovskites with ZnO afforded excellent light-harvesting and charge carrier properties.