We report on experimental demonstration of a wireless temperature sensor node (WTSN) powered by a piezoelectric resonant energy harvesting system. The energy harvesting circuit stores the energy generated by a piezoelectric resonant transducer into a capacitor, and uses the stored energy to power the temperature sensor and its associated signal processing circuits for wireless signal transmission. The main functions of the harvesting system are implemented by discrete components together with a power management application specific integrated circuit (ASIC). The resulting WTSN transmits measured temperature data over a distance of 10m, in real time, and consumes ∼4µW to ∼13µW power (for transmission intervals from 10min to 10s, respectively), which is supplied entirely by the piezoelectric resonant energy harvester.