In this paper, PET (polyethylene terephthalate) films with semiconducting and interface layers were investigated. The electrical properties, such as volume resistivity, tanδ (dissipation factor), and breakdown strength at various temperatures were measured. It is found that the volume resistivity of him (dependence on semiconducting/interface layers) and electrical properties of PET films are changed. Breakdown strength and dissipation factor of PET films with a semiconducting layer (PET/S/PET) are much lower than PET and PET/PET films, due to the increase of charge density or charges between two contacted surfaces in interface/semiconducting layers. It has also been found that the dissipation factor of each film is increased with temperature. For PET/S/PET film, this is dependent on temperature more than PET or PET/PET. However, the breakdown strength is increased up to 85°C and then decreased over 100°C. The electrical properties of PET films with semiconducting/interface layer decrease more than without the layer. This Is a result of temperature dependency, which affects the thermal resistance properties of the PET film much more than the semiconducting/interface layers