Despite the challenges in commercializing large-scale water electrolysis assembled with non-PGM materials, significant progress has been made over the past decade to exploit a number of non-PGM catalysts with remarkable water electrolysis performance, e.g. alloys, carbides, (oxy)hydroxides, intermetallics, oxides, phosphides, sulfides, selenide, and related materials. Among them, the unique d-electron configuration renders transition metal sulfides promising candidates for alkaline water electrolysis. For example, hierarchical nanoassembled MoS2/Co9S8/Ni3S2/Ni has been demonstrated as excellent toward overall water splitting, owing to the facilitated electron transfer properties induced by a strong interface interaction. Regulation of the local electronic structure of Ni3S2 via Fe doping impressively lowers the overpotentials to trigger both the HER and OER under alkaline conditions. Indeed, engineering of structural deficiencies or regulation of crystal phases emerges as an effective strategy to fabricate robust sulfide-based catalysts for effective alkaline electrolyzers. Thus, a variety of transition metal sulfides (TMSs) have been synthesized and examined for overall water splitting.