Flexible magnesium (Mg)–air batteries provide an ideal platform for developing efficient energy-storage devices toward wearable electronics and bio-integrated power sources. However, high-capacity bio-adaptable Mg–air batteries still face the challenges in low discharge potential and inefficient oxygen electrodes, with poor kinetics property toward oxygen reduction reaction (ORR). Herein, spinel nickel cobalt oxides (NiCo₂O₄) nanowires immobilized on nitrogen-doped Ti₃C₂T_x (NiCo₂O₄/N-Ti₃C₂T_x) are reported via surface chemical-bonded effect as oxygen electrodes, wherein surface-doped pyridinic–N–C and Co–pyridinic–N moieties accounted for efficient ORR owing to increased interlayer spacing and changed surrounding environment around Co metals in NiCo₂O₄. Importantly, in polyethylene glycol (PVA)-NaCl neutral gel electrolytes, the NiCo₂O₄/N-Ti₃C₂T_x-assembled quasi-solid wearable Mg–air batteries delivered high open-circuit potential of 1.5 V, good flexibility under various bent angles, high power density of 9.8 mW cm^–2, and stable discharge duration to 12 h without obvious voltage drop at 5 mA cm⁻², which can power a blue flexible light-emitting diode (LED) array and red smart rollable wearable device. The present study stimulates studies to investigate Mg–air batteries involving human-body adaptable neutral electrolytes, which will facilitate the application of Mg–air batteries in portable, flexible, and wearable power sources for electronic devices.