Photocatalytic technology is considered as one of effective approaches to address increasingly serious problems of environment and energy. To boost the photocatalytic efficiency, the innovative cocatalysts have been extensively explored and investigated in recent years. Mo₂C MXene as a new two‐dimensional layer cocatalyst is gained increasing attentions for promoting photocatalytic performance owing to high specific surface area, excellent hydrophilic surface, outstanding metallic conductivity, and flexible adjustability of Mo sites. However, compared with the traditional Ti₃C₂ MXene cocatalyst, Mo₂C MXene has not been fully investigated and systematically summarized in the published articles in the photocatalytic field. In this review, the recent advances about synthesis, modification, photocatalytic applications, and our outlook of the Mo₂C MXene cocatalyst are comprehensively summarized. First, the synthetic methods of Mo₂C MXene are introduced, including top‐down route and down‐top route. Moreover, four modification strategies (constructing heterojunction, doping heteroatom, controlling morphology, and modifying termination) of Mo₂C MXene are illustrated. Subsequently, the photocatalytic applications of Mo₂C MXene cocatalyst in H₂ production, CO₂ reduction, and pollutants degradation are thoroughly discussed. Finally, the crucial challenges and important outlooks of Mo₂C MXene cocatalysts for photocatalytic solar‐to‐fuel conversion are proposed to deliver novel insights and design high‐efficiency Mo₂C MXene cocatalyst‐modified photocatalysts.