Cu-catalyzed electrochemical CO₂ reduction reaction (CO₂RR) to multi-carbon (C₂₊) products is often plagued by low selectivity because the adsorption energies of different reaction intermediates are in a linear scaling relationship. Development of Cu-based bimetallic catalysts has been considered as an attractive strategy to address this issue; however, conventional bimetallic catalysts often avoid metals with strong CO adsorption energies to prevent surface poisoning. Herein, we demonstrated that limiting the amount of Co in CuCo bimetallic catalysts can enhance C₂₊ product selectivity. Specifically, we synthesized a series of CuCo_x catalysts with trace amounts of Co (0.07-1.8 at%) decorated on the surface of Cu nanowires using a simple dip coating method. Our results revealed a volcano-shaped correlation between Co loading and C₂₊ selectivity, with the CuCo_0.4% catalyst exhibiting a 2-fold increase in C₂₊ selectivity compared to the Cu nanowire sample. In situ Raman and Infrared spectroscopies suggested that an optimal amount of Co could stabilize the Cu oxide/hydroxide species under the CO₂RR condition and promote the adsorption of CO, thus enhancing the C₂₊ selectivity. This work expands the potential for developing Cu-based bimetallic catalysts for CO₂RR.