Wearable electronics and sensors for health monitoring are becoming increasingly popular as their functionality continues to grow. Wearable thermoelectric generators (TEGs) are attracting interest due to their ability to self power these electronic devices or sensors by harvesting human body heat. For wearable TEGs, a flexible thermal interface layer (TIL) is used underneath the TEG for wearing on the human body. The large thermal resistance induced at the interface between the skin and the TEG currently limits improvements in the performance of wearable TEGs and needs to be evaluated. This paper develops a numerical model to investigate the performance of wearable TEGs on the curved human wrist. The TEG and bottom TIL are meshed using rectangular grids and the body-fitted coordinate (BFC) transformation, respectively. Using the finite volume method (FVM), the proposed model is calculated, and the temperature and voltage distributions in the TEG and bottom TIL are analyzed. The effects of the radii of curvature of the curved surface, the material properties, and the thicknesses of the TIL are investigated both numerically and experimentally. The results obtained in this research can be utilized for optimal structural designs for wearable TEGs and for material selection of the TIL to enhance the power generation for self-powered electronics.