For the photocatalytic process, the development of efficient photocatalysts is a key and important issue. In recent progress, grafting molecules on the surface of semiconductors via coordination chemistry has received increasing attention owing to its unique advantages. The molecules in molecule-modified semiconductor photocatalysts exhibit three main specific functions, that is, enhancing the light absorption capacity, accelerating charges transfer and improving the surface reaction kinetics; and the regulable structure of molecule has an essential impact on the above functions. In this review, a general introduction to the photocatalysis phenomenon, evaluation and construction of photocatalysts is given first. Then, the type of molecules is introduced; the case studies in typical applications of photocatalytic hydrogen evolution, pollutants removal and carbon dioxide reduction are addressed, focusing on the fabrication, photocatalytic performance and structure−function relationship. In the last section, the underlying challenges and opportunities in future research for molecule-modified photocatalysts are addressed and concluded.