This work reports on the effects of the thermal ageing on the dielectric and physico-chemical properties of polypropylene (PP). The dielectric properties such as AC electrical conductivity (σ ac ), dielectric constant (ε') and dielectric losses (ε") are measured at temperatures between 0 °C and 80 °C in the frequency range of 1 Hz -10 7 Hz. Whereas, the changes in the PP's structure were highlighted by Fourier Transformer Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM) and the estimated Hydophobicity from measuring the contact angle. The experimental results revealed that thermal ageing leads to a degradation of the dielectric properties. Indeed, σ ac , ε' and ε" increased by ageing. These variations may be explained by the changes in the polymers structure 130