The use of low temperature and energy efficient techniques to fabricate composites with tailored interfaces is currently a topic of growing interest. This study reports the proof of concept of a process to fabricate functional multilayer varistor (MLV) devices below 150 °C. In this MLV device, a small volume fraction of polyetherimide (PEI) polymer is used to engineer ZnO grain boundaries, and the multilayer composite is co-fired with base metal internal electrodes via the cold sintering co-fired ceramic (CSCC). The resulting dense nanocomposites MLV and controlled nonlinear current-voltage response of the device confirmed the potential of CSCC. This work also opens up the possibility to fabricate multilayer devices for other types of applications.