SnS₂ nanoparticles have been synthesized using a mild hydrothermal method in the presence of the surfactant sodium dodecyl sulfate (SDS) at 180 °C for 12 h. Physical investigations were carried out to study their structure, size, morphology and optical properties. The x-ray diffraction (XRD) pattern of the as-prepared sample is indexed to the hexagonal phase of SnS₂ and the particle size is 100 nm, which is further confirmed by transmission electron microscopy (TEM). The UV-visible spectrum shows that the absorption edge is blue shifted, and the band gap of the prepared SnS₂ nanoparticles has been evaluated with UV-visible spectroscopy to be 3.54 eV, which is larger than the bulk SnS₂ (∼2.44 eV). The anionic surfactant SDS plays a key role in the formation of the 3D sphere like SnS₂ nanostructures. A probable reaction for the formation of nanocrystalline SnS₂ nanoparticles is proposed.