<p>Copper germanium sulfide-Cu₂GeS₃, is a ternary chalcogenide semiconductor that has attracted significant attention due to its tunable band gap, non-toxic and Earth-abundant elements in its composition, and versatile synthetic routes. However, the poor aqueous solubility of commonly used germanium precursors (GeO₂, GeCl₄) has hindered the development of green synthesis methods for Cu₂GeS₃. To overcome this challenge, we employed a diaquabis (glycolato-O,O′′) germanium(IV) (Ge-GA) prepared in house, as a water-soluble germanium precursor to produce Cu₂GeS₃ nanoparticles through a simple, one-step hydrothermal synthesis method. In addition to the Ge-GA, the hydrothermal synthesis of Cu₂GeS_3, utilizes inexpensive precursors: copper chloride dihydrate and thioacetamide, and leads to nanoparticles crystallizing in a monoclinic structure. The crystallographic and morphological properties were confirmed by X-ray diffraction with Rietveld refinement, Raman spectroscopy, high-resolution transmission electron microscopy (TEM) equipped with electron dispersive X-Ray spectroscopy (EDS), and scanning electron microscopy (SEM) with EDS. Optical characterization revealed a band gap of ~ 1.69&#xa0;eV, while first-principles calculations were used to analyze the band structure and density of states. This work demonstrates the first aqueous synthesis approach of Cu₂GeS₃ nanoparticles, a facile method that could be extrapolated to other Ge-containing compounds. As Cu₂GeS₃ is a semiconductor, this synthesis route opens avenue for its facile translation to optoelectronic, thermoelectric and photovoltaic applications.</p> Graphical abstract