The commercial development of metal-air batteries with remarkably high theoretical energy output is largely limited by the scarcity of low-cost and highly stable electrocatalysts with activities for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) comparable to precious metals and their alloys. Herein, a new inorganic-nanocarbon coupled hybrid, homogeneous NiCo2S4 nanocrystals anchored on nitrogen-doped carbon nanotubes (NiCo2S4/N-CNT), has been developed as an extremely efficient bifunctional catalyst to promote the sluggish ORR and OER kinetics for advanced rechargeable zinc-air battery. It is found that the highest activity is obtained by tailoring the crystal size of NiCo2S4 in the hybrid through tuning the construction of metal-ammonia complexes. The optimized NiCo2S4/N-CNT nanocomposite exhibits extraordinary bifunctional activity through half reaction testing, displaying comparable ORR activity to state-of-the-art carbon supported platinum (Pt/C) and superior OER capability to RuO2 as well as much better durability. The resulting battery performance in generative Zn-air system further confirms its superb effective bi-functionality for catalyzing dual ORR and OER. Compared with those of well-known commercial Pt/C and RuO2, the synergetic NiCo2S4/N-CNT hybrid enables significantly reduced charge-discharge polarization (~0.63V), enlarged energy efficiency (~67.2%) and prolonged cyclability up to 150 cycles at 10mAcm−2. The tremendously enhanced electrochemical behaviors arise from favorable factors including small sized, homogenous dispersed novel NiCo2S4 nanocrystals and coupling interaction between sulfide spinels and underlying N-doped CNT network, which not only provides efficient electron transfer pathway but also alters the electronic structure, thus facilitating the oxygen electrocatalysis during the discharge-charge processes.