© 2018, The Minerals, Metals & Materials Society.In the present study, cadmium sulphide (CdS) nanopowders were prepared by using a simple physical ball milling technique, and their x-ray diffraction (XRD) analysis confirmed the formation of hexagonal wurtzite structure of CdS. The morphology of CdS nanopowders was characterized by scanning electron microscope (SEM). Dielectric and electrical properties of the manufactured Al/(CdS-PVA)/p-Si (MPS) type structures were investigated by capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements as functions of temperature and applied bias voltage at 500 kHz. Some main parameters of the structure such as real and imaginary parts of complex dielectric constants, ε′(= ε′–jε″), loss tangent (tan δ), a.c. electrical conductivity (σac), and real and imaginary parts of complex electric modulus, M*(= M′ + jM″) of the structure were investigated in the temperature range between 230 K and 340 K. Ln(σac)–q/kT curve showed a linear behavior. The value of activation energy (Ea) was obtained as 0.0601 eV at 5.0 V from the slope of this curve. Moreover, argand diagrams of complex modulus were studied to determine relaxation process of these structures.