Since the discovery of graphene, great attention has been paid to transition metal disulfide two-dimensional layered materials due to their exceptional physical and chemical properties. Recently, molybdenum disulfide (MoS₂) quantum dots (QDs) have been extensively investigated because of their unique quantum confinement and boundary effects as well as potential applications in fluorescence imaging, electrochemical catalysis, and biosensors. The preparation of MoS₂ quantum dots can be divided into two types: bottom-up method and top-down method. In order to prepare aqueous MoS₂ QDs solution, in this study, we develop a bottom-up strategy to synthesize MoS₂ QDs using a simple, one-step hydrothermal method with ammonium tetrathiomolybdate [(NH₄)₂MoS₄] as the precursor and hydrazine hydrate as the reducing agent. The morphology and structural characteristics of MoS₂ QDs are analyzed by transmission electron microscopy, and optical properties are characterized using UV-Vis and photoluminescence spectroscopy. Also, the cytotoxicity of MoS₂ QDs are tested. Experimental results demonstrate that MoS₂ QDs can be used for biomedical imaging and drug delivery carriers.