Nickel (Ni) is a promising catalyst for electrochemical urea oxidation reactions. However, its strong chemisorption of CO₂ and the tendency for uncontrollable structural reconstruction during catalysis have limited the exploration of Ni-based catalysts in electrocatalytic urea synthesis. Herein, we propose a co-modification strategy for Ni-mSiO_x using polydopamine (PDA) and polyethyleneimine (PEI) to enable efficient electrocatalytic co-reduction of nitrate and CO₂ for urea synthesis. The incorporation of stable Ni–O–Si active sites effectively balanced competing reaction pathways, while dual polymer modification optimized the surface electronic structure, promoted the formation of pyrrolic/pyridinic nitrogen species (ProN/PN, 86.7%), and accelerated C–N coupling kinetics. The resulting PDA/PEI-Ni-mSiO_x catalyst achieved a urea production rate of 2513 μg·h⁻¹·mg_cat⁻¹, a Faradaic efficiency of 28.6%, and a urea selectivity of 54.2%. Notably, the catalyst retained over 90% of its activity after 39 h of continuous operation, with no observable structural degradation following repeated cycling. This work presents a robust strategy for the rational design of high-performance, durable Ni-based catalysts for urea electrosynthesis and provides mechanistic insights into the structure–activity relationships at polymer–metal oxide interfaces.