Recently, the increase in the CO2 content in the Earth's atmosphere causes global warming and the rapid consumption of fossil fuel resources such as coal and oil. Therefore, effort is required to create clean and sustainable energy resources to address these environmental issues. In this context, hydrogen evolution from water splitting-based photoelectrochemical technologies plays a significant role as a zero CO2 emission fuel. Here, we design and prepare carbon-doped SnO2 nanostructures by a simple single-step thermal decomposition method and coated on a MoS2/p-Si substrate for hydrogen evolution by photoelectrochemical water splitting. The C-doped SnO2/MoS2/p-Si shows enhanced activity in the hydrogen evolution reaction, with an onset potential of −0.17 V at 2.73 mA/cm2, and high stability for over 45 hours. In addition, the doping of carbon influences the shape of the nanostructures, inducing their transformation from cubical rods to polyhedral structures. This study provides a promising method for the fabrication of heterogeneous photoelectrocatalysts for overall water splitting.