CuS nanostructures have been prepared by hydrothermal route using copper nitrate and thiourea as copper and sulfur precursors. Investigations were done to probe the effect of cationic surfactant viz. cetyl trimethyl ammonium bromide on the morphology of the products. Further studies have been done to know the influence of reaction time on the morphology of CuS nanostructures. Results demonstrated that the morphology of CuS was influenced by the reaction time and surfactant. X-ray diffraction pattern showed that the as-prepared CuS nanostructures were in pure hexagonal phase and UV-vis spectra reveal a strong absorption in the visible region of 400-800. nm. A detailed mechanism has been elucidated for the growth of CuS nanostructures. The photocatalytic activity was evaluated by the decolorization of methylene blue (MB) dye under visible-light irradiation and results showed that 87% of the dye was degraded. Thus the as-prepared CuS catalysts are highly promising materials for photocatalytic applications towards dye degradation. © 2013 Elsevier B.V.