Herein, we report a one-step hydrothermal procedure to prepare ZnS-CoS microcomposite which was employed as counter electrode (CE) for dye-sensitized solar cells (DSSCs). The microcomposite exhibits a morphology with ZnS microspheres decorated with CoS nanoparticles, and the decoration effect on electrocatalytic activity of prinstine ZnS toward I-/I-3(-) redox couple was investigated with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel polarization measurements. Experimental results show that ZnS-CoS microcomposite exhibits remarkably enhanced electrocatalytic activity compared with that of pristine ZnS in catalyzing the reduction of I-3(-), and the electrocatalytic activity enhancement closely depends on Co/Zn molar ratio. As a result, the optimized DSSC using ZnS-CoS with a Co/Zn molar ratio of 3: 7 as CE exhibits a highest power conversion efficiency of 6.11%, in comparison with the reference device using Pt CE which shows an efficiency of 7.27%. The enhanced performance compared with DSSC using pristine ZnS CE which has an efficiency of 0.59% can be attributed to the introduction of more electrocatalytic active sites in ZnS-CoS microcomposite. Our study thus provides an effective approach to improve electrocatalytic activity of ZnS and proves its potential suitability as CE for the fabrication of DSSCs. (C) 2015 Elsevier B.V. All rights reserved.