Abstract: The present disclosure concerns a core body temperature sensor for measuring the core body temperature of a body in a non-invasive way via applying the core body temperature sensor to a surface of the bod. The core body temperature sensor comprises: at least a first thermistor pair of opposing thermistors across a first thermal insulator and a second thermistor pair, adjacent to the first thermistor pair, of opposing thermistors across a second thermal insulator, and a means to measure blood perfusion. The core body temperature sensor is an essential planar sandwich structure formed of the at least first and second thermistor pairs across the respective first and second thermal insulators sandwiched between opposing carriers. The present disclosure further concerns a method for determining a core body temperature and a method for the manufacturing of a core body temperature sensor.