The thermal decomposition method is usually used for fabricating Pt counter electrodes for dye-sensitized solar cells (DSSCs). The limitation of the method is its little control over the Pt particle size, agglomeration of the Pt particles on the conductive substrate and poor uniformity of the Pt counter electrodes. Herein, homogeneously dispersed Pt particles on FTO conductive glasses were prepared with an improved thermal decomposition method through adding a small amount of polyvinyl pyrrolidone (PVP) in the Pt precursor solution. The different additional amounts of PVP in the Pt precursor solution could influence the morphologies of the Pt counter electrodes, which further influenced the catalytic activity of the Pt counter electrodes and the photovoltaic performance of DSSCs. An enhanced energy conversion efficiency of the DSSC of about 8.394% was obtained when the Pt counter electrode was prepared with the additional weight amount of PVP 3.5 times that of H₂PtCl₆·6H₂O in the Pt precursor solution, obviously higher than the original 7.062% value of the DSSC with the Pt counter electrode prepared by the traditional unmodified thermal decomposition method on the same loaded low weight of 3.765 μg cm⁻².