In response to the need of stable high-efficiency electrocatalyst for urea oxidation reaction (UOR), a defect-rich (NiFeCu)3S2@(NiFeCu)O core-shelled heterostructure is presented. The core-shelled heterostructure consists of sulfur vacancy (Vs) in the crystalline core and oxygen vacancy (Vo) in the amorphous shell. The Vs enhances the charge transfer, and the Vo contributes to the mass transfer. The unique heterostructure requires only 1.37 and 1.38 V versus reversible hydrogen electrode at 100 and 180 mA cm–2, respectively, and exhibits outstanding cycle stability without potential decay after 12,000 cycles. The structural stability is also contributed by the in situ formation of Cu2O and CuO which was investigated via in situ Raman. The defect-rich (NiFeCu)3S2@(NiFeCu)O core-shelled heterostructure also shows excellent bifunctionality with an electrolyzer cell voltage of 1.47 V at 10 mA cm–2 and 180 h stability. This novel electrocatalyst is highly promising for hydrogen production and also wastewater treatment from urea decomposition.