Global environment and energy crises have become the severe obstacles to socio-economic development and survival environment of mankind. The development of clean renewable energy to replace traditional fossil fuels has become one of the main focuses of today’s society. Converting solar energy into electricity by solar cells represents one of the most promising ways. Among the various solar cell techniques, organic solar cells have attracted much attention for their advantages in light weight, wide range, low cost of raw material sources, good mechanical flexibility, and easy wet-processing for large-area devices. The key to further improve the power conversion efficiency of organic solar cells is developing high-performance electron donor and acceptor materials as well as interfacial materials. Among the organic semiconductors, metal complexes have received considerable research interests owing to their high triplet populations, long exciton lifetimes and high fluorescence quantum yield. In recent years, more and more metal complex-based organic semiconductors have been applied in the field of organic solar cells and obtained high device performances. This review briefly introduces the recent applications of metal complexes in organic solar cells from four aspects of electron donors, electron acceptors, additives and interfacial materials. The “structure-property” relationship of the metal complexes is discussed, and their futural development is also prospected.