The present study investigated the corrosion behavior of coupled active and passive steel bars in a concrete simulated environment. Three different active-to-passive areas (A/P) ratios, i.e., A/P=1/1, 1/3, 1/20, were studied. Three cells were prepared for each group of A/P ratio: an individual cell with active steel specimens, individual cell with passive steel specimens, and a coupled cell that connected active and passive steel bars. All specimens were immersed in a concrete pore solution for 14 days; then, 3 wt.% NaCl was added to the cells. Results of the electrochemical tests indicated that coupling changed the corrosion behavior of the active steel. In the case of A/P=1/1, the corrosion was mainly in the form of localized corrosion, whereas in the case of A/P=1/20, more general and severe corrosion was observed. In addition, the coupling increased the anodic and cathodic Tafel slopes, which are closely related to the iron oxidation rate.