MXene-derived photocatalysts continue to fascinate the research community in developing photo-driven green and sustainable fuel production. However, the efficiency of MXene-derived photocatalyst is still low due to the wide bandgap and high recombination rate of photo-excited charge carriers. Here, we have synthesized the NbC MXene-derived ternary photocatalyst via one-pot in-situ hydrothermal method for photocatalytic hydrogen (H) evolution. The partial oxidation of NbC MXene into NbO nanorods and coupling with InS nanoparticles via in-situ chemical anchoring were the key factors toward high efficiency and long-term stability during photocatalytic H evolution. The optimized ternary photocatalyst composite manifested the highest H evolution efficiency at 68.8 µmol g h, which was 11 and 7.5 times higher than the NbO/NbC (NNC) and pure InS photocatalyst, respectively. Moreover, the photocatalytic stability of the optimized ternary photocatalyst composite was analyzed for five consecutive cycles, and above 87% activity retention was observed even after the fifth cycle without any obvious decline. The separation efficiency of photoexcited charge carriers could be attributed to the synergic effect of the InS/NbO heterojunction and the redox reactions at different sites of the composite. More importantly, the participation of Schottky junction and S-scheme heterojunction charge transfer for the obtained novel ternary photocatalyst was evaluated via ultraviolet photoelectron spectroscopy (UPS) and electron paramagnetic resonance (EPR). This research will provide additional insight into the extended potential of MXene-derived ternary photocatalysts towards efficient H production to meet future global energy demands.