Although single-atom catalysts (SACs) have attracted enormous attention for their applications in the electrochemical reduction of CO2 (CO2RR) due to their extraordinary catalytic activity and well-defined active centers, neighboring effects and their influence on the electrochemical performance of SACs have not been well investigated. In this review, we present a summary of the neighboring effects on SACs for the CO2RR process, where the surrounding atoms not only induce electronic modulation of the metal atom but also participate in the CO2RR. Both theoretical and experimental studies have pointed out that the neighboring sites of the anchored metal center can provide second active/adsorption locations during the catalytic process, enhancing CO2RR performance tremendously. This review supplies advanced insights into the significant roles and impacts of neighboring effects on the catalytic process, which also benefit the development of advanced SACs to achieve efficient electrocatalysis.