Background: ZnO-based varistors are used as surge protectors in electrical circuits. Nonlinear polymer composites are attractive because of their potential applications in low voltage varistors. The aim of this research is to study nonlinear behavior in a new composite containing ZnO, polythiophene and polyethylene. Methods: Sample disks consist of 70 wt% ZnO and 30 wt% polymer matrixes were prepared using the hot press method under 20 MPa at 120 degrees C. I-V characteristics of the disks were studied by applying DC voltage. The structure of the products was examined by FESEM and X-ray diffraction. Results: I-V characteristics of the disks show that their resistivity varies nonlinearly under different voltage. By increasing polythiophene content in sample disks, their breakdown voltage decreases whereas nonlinear coefficient increases. On the other hand increasing press temperature has the same effect on the breakdown voltage and nonlinear coefficient. In addition, each increase in working temperature leads to lower breakdown voltage and nonlinear coefficient. Conclusion: Polymer composite containing 70% ZnO-6% polyethylene-24% polythiophene has an appropriate nonlinear behavior. An increase in press temperature enhances nonlinear coefficient and reduces breakdown voltage. FESEM images of the samples show pressing samples at 120 degrees C does not affect composite structure.