Efficient electron transfer from the counter electrode (CE) to the redox couple electrolyte is the key process in the operation of dye-sensitized solar cells (DSSC). Polythiophene-Iridium oxide (PTh/IrO2) nano composite synthesized by reflux reaction method at different mass ratios (1:4, 1:2 and 1:1) has been explored as an effective electrocatalyst for the triiodide reduction in DSSC. The results of electrochemical impedance spectroscopy (EIS), bode plot studies and Tafel polarization method suggested that the composite synthesized at mass ratio 1:1 exhibited low charge transfer resistance (R ct), faster transport of electrons and excellent electrocatalytic activity. The PTh/IrO 2 composite synthesized at mass ratio 1:1 based DSSC exhibits a conversion efficiency of 3.01%, open-circuit voltage of 0.60 V and a short-circuit current density of 10.1 mA/cm 2. The facile synthesis procedure and attractive electrochemical properties benefit PTh/IrO 2composite to be used as a credible CE in DSSCs.