The electroreduction of CO is a promising technology for carbon utilization. Although electrolysis of CO or CO -derived CO can generate important industrial multicarbon feedstocks such as ethylene, ethanol, n-propanol and acetate, most efforts have been devoted to promoting C-C bond formation. Here, we demonstrate that C-N bonds can be formed through co-electrolysis of CO and NH with acetamide selectivity of nearly 40% at industrially relevant reaction rates. Full-solvent quantum mechanical calculations show that acetamide forms through nucleophilic addition of NH to a surface-bound ketene intermediate, a step that is in competition with OH addition, which leads to acetate. The C-N formation mechanism was successfully extended to a series of amide products through amine nucleophilic attack on the ketene intermediate. This strategy enables us to form carbon-heteroatom bonds through the electroreduction of CO, expanding the scope of products available from CO reduction.