The thermal characteristics of bi-tapered thermoelectric generator are investigated. The influence of the dimensionless shape parameter, associated with the device pin geometric configuration, on the first-and second-law efficiencies and device output power is examined. The study is extended to include the effects of the external load parameter and the device operating temperature ratio on the device characteristics. It is found that the first-law efficiency is not considerably influenced by the dimensionless shape parameter; however, the second-law efficiency and the device output power are significantly affected by the shape factor. The external load parameter has an adverse effect on the first-and the second-law efficiencies and the device output power. In this case, increasing external load parameter lowers the thermal performance of the thermoelectric generator. Reducing operating temperature ratio improves the first-and the second-law efficiencies and the device output power significantly.