Hypothesis: Accurate temperature measurement is of particular importance in various medical and industrial fields. Researchers have recently developed heat-sensitive sensors with the development of nanotechnology. The goal of the present research is the fabrication of an ultra-sensitive thermal nanosensor that can be applied to monitor human body temperature and industrial tasks. Methods: For this purpose, polypyrrole and graphene nanocomposites were synthesized with different percentages. The structural characteristics of the obtained nanocomposites were assessed by electron scanning microscopy and X-ray diffraction spectroscopy (XRD). Findings: The results showed that synthetic graphene and polypyrrole are in the shape of sheets and fiber with a thickness less than 100 nm and diameter of 150 nm, respectively. The XRD spectrum of the 0. 5% (by wt) nanocomposite also indicated a suitable combination of graphene and polypyrrole. The thermal biosensor evaluations of samples disclosed that pure polypyrrole allocated the first rank compared to other samples in the temperature range of 25-80°, C, with a sensitivity of 218 kΩ, /°, C, but its nonlinear behavior limited its applicability. In this temperature range, 0. 5% (by wt) nanocomposite sensor showed the highest optimal performance with the sensitivity, temperature coefficient resistance (TCR), response and recovery time of 197 kΩ, /°, C,-1. 17 %°, C-1, 78 and 170 s, respectively. In the temperature range of 35-40°, C, to control the human body temperature, the nanocomposite sensor with the concentration of 0. 5% (by wt) has the best linear performance with a sensitivity of 20. 5 kΩ, /˚, C, TCR of-2. 26% per°, C and response and recovery times of 21 and 34 s. In comparison to similar samples, this nanocomposite has improved by 23. 9 and 1. 8 times, with respective to the above recovery time. In the final conclusion, the nanocomposite sensor with a concentration of 0. 5% (by wt) was designated as the most ideal nanosensor that can be utilized in industrial as well as medical fields.