In this study, we report on the preparation of a copper oxide/strontium titanate/multi-walled carbon nanotubes (CuO/STO/MWCNTs) photocatalyst and their photocatalytic activity for dye degradation under visible light. The CuO/STO/MWCNTs nanocomposites were synthesized via a sequential three-step process of sol-gel, impregnation and mixing in aqueous medium methods. The obtained nanocomposites were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX),  UV–vis diffuse reflectance spectroscopy (DRS), transmission electron microscope (TEM), dark field scanning transmission electron microscope (DF-STEM-EDX mapping) and X-ray photoelectron spectra (XPS). The effect of CuO-content on structural, properties and photocatalytic activity of CuO/STO/MWCNTs nanocomposites for the degradation of methylene blue (MB) under visible light irradiation was studied.