Developing electrocatalysts with fast kinetics and long-term stability for alkaline hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) is of considerable importance for the industrial production of green and sustainable energy. Here, an ultrathin Ir-Sb nanowires ( Ir-Sb NWs) protected by antimony oxides (SbO_x) was synthesized as an efficient bifunctional catalyst for both HOR and HER under alkaline media. Except from the much higher mass activities of Ir-Sb nanowires than those of Ir nanowires (Ir NWs) and commercial Pt/C, the SbO_x protective layer also contributes to the maintenance of morphology and anti-CO poisoning ability, leading to the long-term cycling performance in the presence of CO. Specifically, the Ir-Sb NW/SbO_x exhibits the highest catalytic activities, which are about 3.5 and 4.8 times to those of Ir NW/C and commercial Pt/C toward HOR, respectively. This work provides that the ultrathin morphology and H₂O-occupied Sb sites can exert the intrinsic high activity of Ir and effectively optimize the absorption of OH* both in alkaline HER/HOR electrolysis.