A highly sensitive carbon dioxide (CO2) sensor based on light-induced thermoelastic spectroscopy (LITES) utilizing a self-designed low-frequency quartz tuning fork (QTF) and a fiber-coupled multipass cell (MPC) is reported in this paper. The QTF with low resonant frequency of 8675 Hz and high Q factor of 11675.64 was used to improve its energy accumulation time and the sensor’s signal level. The MPC with fiber-coupled structure and optical length of 40 m was adopted to significantly increase the gas absorbance and reduce the optical alignment difficulty as well as improve the robustness of the sensor system. A distributed feedback (DFB), near-infrared diode laser with emission wavelength of 1.57 µm was used as an excitation source. The experimental results showed that this CO2-LITES sensor had excellent linear response to CO2 concentrations. The minimum detection limitation (MDL) of this CO2-LITES sensor was obtained to be 445.91 ppm and it can be improved to 47.70 ppm when the integration time of the system reached 500 s. Further improvement methods for detection performance of such sensor were discussed.