Cobalt sulfide counter electrodes for the dye-sensitized solar cell (DSSC) were successfully prepared on fluorine-doped tin oxide (FTO) glass substrates by a facial one-step in situ solvothermal method. The influences of prepared temperature on the synthesized phase, surface morphology, electrocatalytic, and photovoltaic performances of the cobalt sulfide counter electrodes were investigated with X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Tafel, and photocurrent density-voltage (J-V) measurements. The results indicated that very thin Co9S8 nanoparticle thin films grew on the FTO substrates and the Co9S8 counter electrode prepared at 180 A degrees C showed superior electrocatalytic activity, chemical stability, and photovoltaic performance. The DSSC based on the Co9S8 counter electrode prepared at 180 A degrees C exhibited an efficiency of 6.59 % which was comparable to the solar cell based on the sputtering Pt counter electrode (6.82 %). It indicated that Co9S8 in situ growing on FTO glass substrate at 180 A degrees C is a potential candidate to replace Pt as a low-cost and efficient counter electrode of DSSC.