Electroreduction of NO3- and CO2 to urea (ENCU) represents a fascinating strategy to enable waste NO3-/CO2 removal and sustainable urea production. Herein, uncoordinated Zn nanosheets (U-Zn) are developed as a highly selective ENCU catalyst, exhibiting the highest urea-faradaic efficiency of 31.8% with the corresponding urea yield rate of 39.3 mmol h-1 g-1 in a flow cell. Theoretical calculations and electrochemical spectroscopic measurements reveal that the high ENCU performance of U-Zn arises from the critical role of uncoordinated Zn sites that can promote both key steps of *NO2/CO2 coupling and *CO2NH2 protonation to *COOHNH2, while retarding the competitive side reactions.