The ternary cobalt diindium sulfide (CoIn2S4) counter electrode (CE) with interconnected nanosheet array structure is fabricated on the fluorine-doped tin oxide (FTO) substrate by in situ ethanol solvothermal synthesis. The ethanol solvent and In2.77S4 intermediate play important roles on the formation of the interconnected nanosheet array structure. The dye-sensitized solar cell (DSSC) with the optimized ternary CoIn2S4 CE gives an energy conversion efficiency of 8.83%, which is much higher than that of DSSCs based on the binary CoS2 (6.47%), and In2.77S4 (0.46%) CEs and can be comparable with that of Pt CE (8.19%) under full sunlight illumination (100 mW cm(-2), AM 1.5 G). Except for the intrinsically electrocatalytic activity from the CoIn2S4, the higher conversion efficiency of CoIn2S4 based DSSC can be attributed to that the interconnected nanosheet array structure provides plentiful catalytic active sites, abundant electron transport channels, and fast electrolyte diffusion.