Co-based single-atom-catalysts have emerged as possible candidates for the oxygen evolution reaction (OER); however, further improvements in the performance of Co metal sites are challenging with limited optimization space. In this study, a Co-Fe dual-atomic catalyst with optimized intrinsic OER performance was designed, where the individual roles of the single metal sites were investigated in detail. The optimized dual-atomic catalyst exhibited OER activity with an overpotential of 240 mV and turnover frequency (TOF) of 146 s−1 (10 mA cm−2). The systematic microscopy and impedance investigations revealed that the interplay between the Co and Fe metal sites is the key factor for the improved OER performances, wherein the Co sites act as the active sites, with the adjacent Fe serving as the co-catalytic site. Density functional theory (DFT) calculations corroborated the strong orbital coupling between Fe and Co, leading to a d-band structure with improved electroactivity. The Co site coordinated with S and N, enabling efficient site-to-site electron transfer, while the Fe site coordinated with N, which facilitated the chemical stability of the Co site to guarantee efficient OER activity. This work supplied an in-depth understanding of the electrocatalytic performances of dual-atomic catalysts, which is further beneficial for the design of novel atomic catalysts with superior electroactivity towards the OER.