Flexible thermoelectric generators (f-TEGs) can directly convert low-grade thermal energy from the human body and surrounding environment into electricity, showing great promise for wearable power systems and self-sustained sensors. However, conventional inorganic thermoelectric materials still face significant constraints in balancing flexibility, structural stability, and energy conversion efficiency. In this work, high-performance Bi₂Te₃/hydroxypropyl methylcellulose (HPMC)@paper composite thermoelectric films were fabricated via a vacuum filtration method, realizing a synergistic enhancement in both flexibility and thermoelectric performance. The obtained p-type and n-type films exhibited Seebeck coefficients of 182.96 and −229.98 μV·K⁻¹, respectively, and maintained stable output under repeated bending. Based on these films, both planar and multilayer stacked f-TEG architectures were designed to achieve multidimensional energy harvesting. The Level-III stacked f-TEG reached an ultrahigh device-level Seebeck coefficient (S_device) of 11,330.25 μV·K⁻¹ and a maximum output power of 617.4 nW, demonstrating outstanding conversion capability and structural robustness. When integrated with an Ecoflex substrate, the device maintained stable operation under bending, twisting, and conformal attachment to curved surfaces. A smart wristband built from this system continuously drove a low-power pedometer during human-wear testing, validating its feasibility for wearable thermoelectric energy harvesting. This study proposes an inorganic–organic hybrid thermoelectric film design that combines high flexibility with excellent thermoelectric performance, offering a new strategy for flexible energy devices and showing broad prospects in wearable electronics.