In this paper, we present the fabrication of an expanded-perlite (EP)-based floating photocatalyst comprising CdS and Ag nanoparticles. In the Ag-CdS/EP nanocomposite, Ag-CdS was introduced as the photocatalytically active components and EP was employed as a low cost and sustainable support to reduce the problem of easy aggregation and improve the floating behavior of the designed catalyst. The Ag-CdS/EP photocatalyst was characterized via transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-vis diffuse spectroscopy (UV-vis DRS), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) and photoelectrochemical measurements. The XRD and HR-TEM results confirmed the formation of cubic crystalline silver nanoparticles anchored on the surface of EP-immobilized hexagonal cubic CdS. The significantly enhanced photocatalytic activities of the Ag-CdS/EP nanocomposite with varying Ag contents were investigated for the degradation of rhodamine B (RhB) and phenol under visible light irradiation, and it was found that the photocatalytic reaction proceeds via first order kinetics. Furthermore, the desirable cycling ability (5 runs) of the Ag-CdS/EP photocatalyst indicates its promising stability and reusability. The designed novel photocatalyst also conforms to the development of green chemistry since no organic solvents were required.