Photocatalysts have gained much attention because of the water pollution instigated by the rapid usage of organic dyes for industrial needs. The degradation of these dyes using photocatalysts under natural light is an economical and popular method for water treatment. There is a need to synthesize photocatalytic materials which can generate reactive oxygen species under natural light. Hence, keeping in mind the above point, rose flower-shaped CuS nanostructures have been synthesized first time by solvothermal technique by varying reaction duration. The self-assembled powder of CuS nanostructures is characterized using XRD, FE-SEM, TEM, DLS, EDS, XPS, Raman, FT-IR, and UV–visible spectroscopy. The XRD and TEM analyses confirmed the formation of a polycrystalline hexagonal structure with prominent diffraction peaks. FE-SEM study shows the formation of uniformly self-assembled rose flower-shaped nanostructures of size 2–3 μm composed of densely packed nanoparticles. XPS study shows the presence of Cu(II) and Cu(I) states of copper in the synthesized batch and stoichiometric composition Cu:S is found to be 60:40 at.%. The optical studies showed broad absorption spectra of CuS nanostructures in about 300–800 nm wavelength range. Besides, this work studies the degradation activity of methylene blue and crystal violet organic dyes under natural sunlight conditions without the presence of any additive agent. [ABSTRACT FROM AUTHOR]