The development of electrocatalysts with excellent performance, affordable price, and abundant reserves is an important way to realize the overall water splitting. In this study, we design a unique preparation process to form a carbon-coated Co/Co9S8-MoS2 bifunctional catalyst. Excessive H2S generated in the decomposition process of ammonium thiomolybdate can partially sulfurize carbon-coated Co nanoparticles, and Co/Co9S8 mixed phases will be formed on MoS2. The as-prepared catalyst possesses good bifunctional electrocatalytic activity under the alkaline environment for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The amorphous carbon-coated Co/Co9S8-MoS2 composite shows a low overpotential of 128 mV for HER and 325 mV for OER in 1 M KOH solution, respectively. Besides, the amorphous carbon shell can prevent Co/Co9S8 nanoparticles from corrosion, and the catalyst shows remarkable long-term cycle stability.