The rising level of atmospheric CO2 caused by increased fossil energy consumption is linked to global warming effects. Electrochemical CO2 reduction (CO2RR) can convert CO2 into value-added chemical fuels by using renewable energy-generated electricity as the energy input, providing a promising solution to mitigate the CO2 emissions. Compared to conventional precious metal catalysts for CO2RR, carbon-based catalysts are made of earth-abundant elements and less expensive, with great potential for large-scale applications. In this Review, recent advances of designing and synthesizing nitrogen coordinated single atomic transition metals supported on nanocarbons (M−NX-C; M=Fe, Ni, Co) as electrocatalysts for CO2RR are reviewed from both experimental and computational aspects. The catalytic mechanisms and design principles are highlighted, and the correlations of catalyst synthesis-structure-performance relationships are discussed. The disparities in catalytic activity between noble metal catalysts (Ag and Au) and M−NX-C catalysts suggest that there is still much room to develop more advanced M−NX-C catalysts. Therefore, several strategies, including mechanism exploration, M−NX sites and carbon supports engineering, and large-scale fabrication of atomically dispersed catalysts and reactor systems design are proposed to propel the use of M−NX-C for achieving high-efficient and costeffective CO2-to-fuels conversion.