Electrocatalytic nitrate (NO3-) reduction has emerged as an attractive dual-function strategy to produce ammonia (NH3) and simultaneously mitigate environmental issues. However, efficient electrocatalysts with high selectivity for NH3 synthesis are highly desired. In this work, we report the Co-NCNT nanohybrid as a highly active electrocatalyst towards NO3--to-NH3 conversion. In 0.1 M NaOH solution containing 0.1 M NO3-, the Co-NCNT catalyst is capable of attaining a large NH3 yield of 5996 μg h-1 cm-2 and a high faradaic efficiency of 92% at -0.6 V versus reversible hydrogen electrode. Moreover, it displays excellent electrochemical stability.