Triboelectric nanogenerators (TENGs) are promising candidates for energy harvesting, portable devices, and self-powered sensing systems, owing to their simplicity and high efficiency. However, their practical deployment in high-temperature environments is constrained by their performance degradation due to thermionic emissions, surface charge dissipation, and thermal distortion. In this study, we developed a thermally robust TENG that maintained stable operation up to 160 °C by incorporating cordierite (Crd; 2MgO·2Al 2O 3·5SiO 2) into a polyimide (PI) matrix. The optimized 5   wt% Crd–PI composite exhibited a 1.5-fold increase in open-circuit voltage and a two-fold increase in short-circuit current compared to those of pristine PI films, while retaining excellent thermal stability. Notably, the device delivered a consistent output voltage of ±2   V at 96   Hz and 90 °C, mimicking vehicle engine operating conditions. The outstanding high-temperature performance is attributed to the inherent thermal durability of Crd, which exhibits zero thermal expansion, a stable crystal structure, and permittivity retention up to 240 °C. These results demonstrate the feasibility of using the Crd–PI composites in thermally demanding environments. These composites are compelling alternatives to conventional vibration sensors for automotive and industrial applications. This study highlights the critical role of ceramic–polymer composites in advancing high-temperature operable TENG technologies.