This study reports on the synthesis of bimetallic PtAu nanoparticles (NPs) on the transparent conducting oxide electrode by using dry plasma reduction under atmospheric pressure without using any toxic chemicals and at a low temperature, which are first employed as counter electrodes (CEs) for efficient dye-sensitized solar cells (DSCs). High resolution scanning electron microscopy (HRSEM) and x-ray photoelectron spectroscopy (XPS) are utilized for analyzing the morphology and the chemical composition of bimetallic PtAu NPs. The highest catalytic activity of the bimetallic PtAu NP CE is found through an optimization of the volume ratio of Au and Pt precursors used for synthesis of NPs. As a result, the highest electrocatalytic performance, which corresponds to the lowest charge transfer resistance of 0.88 Ω, is obtained at the Au and Pt precursor molar ratio of 1. The DSC employing Pt_0.5Au_0.5 alloy CE achieved a maximum efficiency of 8.0% among all cells under study. The efficiency is higher than those of 7.4%, and 0.1% for Pt NPs and Au NPs – based DSCs, respectively. The obtained results establish a base for the potential use of PtAu alloy CEs in efficient and robust DSCs.