Molybdenum disulfide (MoS₂), an attractive material for energy conversion devices, is known to exhibit varying properties depending on the number of layers and the phase structure. In this study, we developed a supercritical hydrothermal process that allows the controllable synthesis of MoS₂ nanosheets with various structural and morphological characteristics. Detailed characterization of the synthesized materials confirmed that the number of layers in the MoS₂ nanosheets could be controlled by varying the organic reducing agent under supercritical hydrothermal conditions. In addition, the MoS₂ phase could be controlled kinetically by varying the reaction time with ascorbic acid as the reducing agent. Because water and elemental sulfur were respectively used as the solvent and sulfur source and as the reaction time was minimal, the developed hydrothermal process represents a facile processing method for different types of MoS₂ nanosheets.