In this study, the newly synthesized polyaniline (PANI)/polyethylenimine modified nitrogen doped graphene quantum dot (PN-GQD)/tungsten oxide (WO₃) ternary composites were used as ammonia (NH₃) gas sensor detected the NH₃ at room temperature. Fourier transform infrared spectrometer, field-emission scanning electron microscopy, transmission electron microscopy, and x-ray photoelectron spectroscopy were applied to illustrate the chemical structure and morphology of the fabricated ternary composites. The NH₃ gas-sensing performances of PANI/PN-GQD/WO₃ composite sensor were determined in the concentration between 0.6 and 2.0 ppm at room temperature and the response value of the ternary composite sensor with an exposure of 1.0 ppm NH₃ was 19.9, which was much better than those of PANI and PANI/WO₃ sensors. Because their highly sensitive detection of NH₃ ranging from the concentration between 0.6 and 2.0 ppm at room temperature, the PANI/PN-GQD/WO₃ composite sensor was confirmed to be extremely effective to detect the kidney or hepatic disease from the human breath. This ternary composite sensor with an exposure of 1.0 and 2.0 ppm NH₃ also displayed extraordinary repeatability and selectivity at room temperature. According to these findings, this fabricated PANI/PN-GQD/WO₃ composite sensor will be an excellent gas-sensing material to detect the kidney or hepatic disease from the human breath.