Thermoplastic polyurethane (TPU)/bacterial cellulose-based carbon nanofiber (BC-CNF) electric heating pads were successfully fabricated and evaluated for their properties. First, humic acid dyed-bacterial cellulose (BC) was carbonized at 900 °C for 2 h to obtain BC-CNF. The resulting BC-CNF underwent size reduction and sulfonation with H2SO4, producing fine sulphonated carbon particles (BC-CNF-SO3−) with improved dispersibility in hydrophilic media. To enhance compatibility with hydrophobic TPU matrix, complexation with cationic surfactant (CTAB) was performed, forming the BC-CNF-SO3−+CTAB complex. A flexible TPU/BC-CNF heating pad containing up to 33 wt% BC-CNF was fabricated using the solvent casting technique. Electrothermal performance was assessed by applying 5, 9, and 12 V while measuring temperature profile between cathode and anode. After 1 min, the heating pad reached temperatures of 37.4, 55.0, and 61.8 °C, respectively. These results highlight the potential of TPU/BC-CNF composites for application in flexible electric heating pads, particularly for therapeutic heat treatment.