In this study, novel Ag/AgBr/graphene oxide (GO) nanosheets were successfully prepared via a facile and fast sonochemical route for the first time, and ultrasound has a key role in the preparation process. Ag nanoparticles were formed on the surface of cubic AgBr in the composite by photo-reduction through sunlight irradiation. The physical and photophysical properties of the as-prepared Ag/AgBr/GO nanocomposite were characterized using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis diffuse reflection spectroscopy (DRS) and Raman spectroscopy techniques. Moreover, the Ag/AgBr/GO nanocomposite exhibited excellent photocatalytic activity under sunlight illumination to decompose diclofenac sodium (DCF), which is an important pharmaceutical pollutant. The decomposition of DCF by the sonosynthesized sample was done within 6 min, which may be attributed to its large surface area as well as superior charge separation and transfer efficiency. Furthermore, the COD and stability of the catalyst were investigated.