The applications of copper and copper-based nanoparticles as catalysts have generated a great deal of interest in recent years because copper is inexpensive and earth abundant. However, direct conversion of carbon dioxide to fuels and chemicals remains a grand challenge in electrochemical reduction of CO₂. Here we report a simple synthetic strategy on nitrogen-doped copper nanoparticles, and investigate the effect of doping amount on the products of CO₂ reduction reaction. When the alkylamine is bound to a copper surface, the scission of C-N bond on the particles surface appears to provide nitrogen source to further react with copper nanoparticles through Ostwald ripening process. Compared to pure copper nanoparticles, nitrogen doping not only improves oxidation resistance, but also facilitates multiple proton and electron transfers to synthesize multicarbon products during CO₂ reduction reaction. Furthermore, we envision that such unique doping strategy could be extended to the design of other inorganic nanoparticles for various catalytic applications.