The thermal characteristics of natural fiber-reinforced polymer (NFRP) composites are crucial for real-world applications. The current study investigated the consequence of embedding human hair on the thermal attributes of NFRP hybrid composites. Two distinct polyester composites were developed by the hand lay-up method using 3–4 mm-long fibers and 20% (vol.) fiber loading. The first one is made of BNH and jute fibers with a 1:1 ratio (non-implanted) and the other is made of BNH (betel nut husk) and jute fibers and human hair with a 1:1:1 ratio (hair-implanted). Their thermal characteristics are investigated and compared. The thermal conductivity, thermogravimetric (TGA), differential thermogravimetric (DTG), and thermomechanical (TMA) analysis of composites are accomplished. The differential thermal analysis (DTA) explored the composite’s inflection points and endothermic peak temperature. TMA analysis unveiled the dimensional stability, coefficients of thermal expansion (CTE), and glass transition temperature (Tg) of both composites. The temperature for maximum mass loss is also predicted using the DTG curve. Human hair-implanted composites exhibit higher thermal stability, fire-deterrent properties, and glass transition temperature, and lower CTE than non-implanted ones. Outcomes are validated through mechanical characteristics and by investigating the morphological properties of composites. It revealed that human hair enhances the thermal characteristics of NFRP composites. It can be embedded in the NFRP composites as a low-cost, plentiful, and easily reachable constituent to prevent environmental contamination, enhance sustainability, and improve the composite’s thermal stability. Eventually, it will promote the adoption of NFRP composites over synthetic fiber-reinforced composites across various fields.