In this study, CuInS₂/ZnS nanocrystals were synthesized by a two-step mechanochemical synthesis for the first time. In the first step, tetragonal CuInS₂ was prepared from copper, indium and sulphur precursors. The obtained CuInS₂ was further co-milled with zinc acetate dihydrate and sodium sulphide nonahydrate as precursors for cubic ZnS. Structural characterization of the CuInS₂/ZnS nanocrystals was performed by X-ray diffraction analysis, Raman spectroscopy and transmission electron microscopy. Specific surface area of the product (86 m²/g) was measured by low-temperature nitrogen adsorption method and zeta potential of the particles dispersed in water was calculated from measurements of their electrophoretic mobility. Optical properties of the nanocrystals were determined using photoluminescence emission spectroscopy.