A facile one step in-situ solvothermal synthesis method has been used to synthesize CdS nanoparticles (NPs), graphene oxide (GO), reduced graphene oxide (rGO) and rGO decorated with highly dispersed CdS NPs. The optical properties of synthesized samples have been investigated using ultraviolet visible (UV-VIS) spectroscopy, photoluminescence (PL) spectroscopy and Raman spectroscopy (RS) techniques and a comparative analysis of the results obtained by these techniques have been done. The CdS NPs decorated over rGO sheet act as an external perturbation that causes to split 2D Raman band into two distinct Raman peaks. The presence of two distinct Raman peaks in 2D band indicates that the synthesized rGO could be composed by double layers. The room temperature ferromagnetism (RTFM) of CdS NPs decorated over rGO is decreased compared to pure CdS NPs. The rGO-CdS nanocomposites show enhanced photocatalytic activity for the degradation of methylene blue (MB) dye than that of the pure CdS NPs. The improved photocatalytic activity of rGO-CdS nanocomposites could be attributed to the transfer of electron from conduction band (CB) of CdS NPs to the rGO sheets. It causes to increase the amount of (OH)-O-center dot and O-2(center dot-) radicals in the aqueous solution of dye, which react with MB dye and degrade it. Due to enhanced photocatalytic activity and coercivity, the rGO-CdS nanocomposites may be used for many practical applications in future nanotechnology. (C) 2015 Elsevier B.V. All rights reserved.