Flexible thermoelectric (TE) technology can convert human-body heat into electricity, showing great promise for powering wearable devices. Achieving simultaneous excellent flexibility and high TE performance is still a big challenge for both inorganic and organic-based flexible TE materials. Here, to overcome this challenge in the well-known Bi₂Te₃-based materials, we propose an anisotropy engineering strategy triggered by nanostructuring design and excess Te addition. A two-step solution-synthesis method is developed to prepare patchwork-like Bi₂Te_2.7Se_0.3 nanorods, which can be assembled into flexible thin films by the screen-printing and spark-plasma-sintering process. Owing to the weakened anisotropy by nanostructuring, our nanorods-derived Bi₂Te_2.7Se_0.3 thin films exhibit excellent bending flexibility. Further introducing excess Te can optimize the anisotropy as well as the interfacial connecting and oxidation resistance of these thin films. Consequently, a high power factor of ∼745 μWm^-1K^-2 at room temperature can be achieved in the n-type Bi₂Te_2.7Se_0.3 thin film with 10% excess Te. These n-type thin films are further assembled with p-type legs (Bi_0.5Sb_1.5Te₃ with 4% excess Te) into a 5-pair TE device with good flexibility and stability, showing a maximum power density of ∼6.06 Wm^-2 at a temperature difference of ∼28.3 K. This work indicates that anisotropy engineering in solution-derived nanostructured thin films can be a facile way to balance the flexibility and TE properties, further advancing flexible TE devices.