This study presents the development of a novel ionic thermoelectric film with high flexibility, stability, and thermoelectric performance. The film, composed of carbon-based materials (graphene oxide, GO), ionic liquid, and cross-linked polymer, exhibits excellent thermoelectric properties with a Seebeck coefficient (S) of −76.7 mV K⁻¹, a power factor (S²σ) of 753.0 μW m⁻¹ K⁻², and a dimensionless figure-of-merit (ZT) of 0.19 at 383 K. The film also demonstrates outstanding mechanical properties, including a tensile strength of 219.7 kPa, elongation at break of 389%, Young’s modulus of 84.1 kPa, toughness of 0.4 MJ m⁻³, and flexibility to bend at 180°. Importantly, the film maintains its performance even after being exposed to air for 7 days. Based on these properties, a miniature 9-legged flexible thermoelectric device was fabricated, achieving an optimal output power density of 1.32 mW cm⁻² with a temperature difference of 20 K. This work provides a promising approach for the design of long-term, high-performance ionic thermoelectric materials and easily integrable flexible devices.This study presents the development of a novel ionic thermoelectric film with high flexibility, stability, and thermoelectric performance. The film, composed of carbon-based materials (graphene oxide, GO), ionic liquid, and cross-linked polymer, exhibits excellent thermoelectric properties with a Seebeck coefficient (S) of −76.7 mV K⁻¹, a power factor (S²σ) of 753.0 μW m⁻¹ K⁻², and a dimensionless figure-of-merit (ZT) of 0.19 at 383 K. The film also demonstrates outstanding mechanical properties, including a tensile strength of 219.7 kPa, elongation at break of 389%, Young’s modulus of 84.1 kPa, toughness of 0.4 MJ m⁻³, and flexibility to bend at 180°. Importantly, the film maintains its performance even after being exposed to air for 7 days. Based on these properties, a miniature 9-legged flexible thermoelectric device was fabricated, achieving an optimal output power density of 1.32 mW cm⁻² with a temperature difference of 20 K. This work provides a promising approach for the design of long-term, high-performance ionic thermoelectric materials and easily integrable flexible devices.