•A novel structural design of the wearable TEG to harvest body heat is developed.•The TEG features excellent flexibility and high power generation for body heat harvesting.•A miniaturized accelerometer is powered by the TEG to detect body motion through harvesting wrist heat. Wearable thermoelectric generators (TEGs) enable the conversion of human body heat into microwatts to milliwatt electricity, which can be utilized to power miniaturized electronic devices for motion detection and healthcare monitoring. This paper presents a novel wearable TEG with 52 pairs of cubic-shaped thermoelectric legs to harvest human body heat. The thermoelectric legs are made of P-type and N-type Bi2Te3-based powder materials, and are connected electrically in series through soldering. The flexible printed circuit board (FPCB) with special holes is designed and used as substrate to enhance the flexibility of the TEG for wearable applications. The performances of the TEG, including the bulk thermoelectric legs, are characterized. The results show that the TEG can generate an open-circuit voltage of 37.2 mV at ΔT = 50 K, and the internal resistance of the TEG is quite low at a value of 1.8 Ω. Then the TEG was worn on a human wrist to harvest body heat and power a 3-axis miniaturized accelerometer for detection of body motion at ΔT = 18 K. The results demonstrate that the developed wearable TEG features high output performance and could be utilized for powering electronics and/or sensors by harvesting human body heat.