Abstract: Transition metal phosphides (TMPs) have exhibited decent performance in an oxygen evolution reaction (OER), which is a kinetic bottleneck in many energy storages and conversion systems. Most reported catalysts are composed of three or fewer metallic components. The inherent complexity of multicomponent TMPs with more than four metallic components hinders their investigation in rationally designing the structure and, more importantly, comprehending the component-activity correlation. Through hydrothermal growth and subsequent phosphorization, we reported a facile strategy for combining TMPs with tunable elemental compositions (Ni, Fe, Mn, Co, Cu) on a two-dimensional titanium carbide (MXene) flake. The obtained TMPs/MXene hybrid nanostructures demonstrate homogeneously distributed elements. They exhibit high electrical conductivity and strong interfacial interaction, resulting in an accelerated reaction kinetics and long-term stability. The results of different component catalysts’ OER performance show that NiFeMnCoP/MXene is the most active catalyst, with a low overpotential of 240 mV at 10 mA·cm⁻², a small Tafel slope of 41.43 mV·dec⁻¹, and a robust long-term electrochemical stability. According to the electrocatalytic mechanism investigation, the enhanced NiFeMnCoP/MXene OER performance is due to the strong synergistic effect of the multi-elemental composition. Our work, therefore, provides a scalable synthesis route for multi-elemental TMPs and a valuable guideline for efficient MXene-supported catalysts design.