In this work, Co8FeS8/CoS heterostructural nanoparticles anchored on carbon nanotubes (CNTs) network are synthesized via a novel “microwave-assisted bubble bursting” synthesis strategy. By using a microwave-assisted reaction and particularly the bubble bursting effect caused by the mixed solvent (ethylene glycol and DI water), ultrathin Co8FeS8/CoS heterostructural nanoparticles homogeneously grown on orderly rearranged and highly conductive CNT skeleton. As an OER catalyst, the Co8FeS8/CoS@CNT delivers an ultralow overpotential of only 278 mV for 10 mA cm−2, a very small Tafel slope of 49 mV dec−1, and excellent long-term stability, which is attributed to its highly conductive CNT-based porous nanoarchitecture, and particularly the uniform distribution of Co8FeS8/CoS heterostructural nanoparticles. This work provides a promising strategy for rational design and time-saving and environment-friendly synthesis of low-cost transition metal-based hybrid electrocatalysts as well as maximizing the catalytic potential for not only limited to metallic sulfide but probably also other kinds of catalytic materials.