Electrochemical dechlorination of 1,2-dichloroethane (DCE) is one of the prospective and economic strategies for the preparation of high-value ethylene. However, the exploration of advanced electrocatalysts with high reactivity and selectivity and the identification of their active sites are still a challenge. Herein, a single-atom (SA) Fe–Nx–C nanosheet with the presence of a highly efficient Fe–N4 coordination pattern is reported. The as-prepared single-atom electrocatalyst exhibits a higher reactivity and ethylene selectivity for DCE dechlorination reaction than those of the commercially adopted 20% Pt–C catalyst. By a combination of experiments and theoretical calculations, the atomically dispersed Fe center in the Fe–N4 structure was unveiled to be the dominating active site for electrochemical production of ethylene. Our work would offer an approach for the rational development of SA materials and supply crucial insight into the mechanism of ethylene production through the DCE dechlorination reaction.