In this letter, a new temperature-compensated internal LNA noise calibration source for system temperature monitoring is presented. It is easily integrated into amplifiers and has a negligible impact on the noise performance. The power level of the proposed calibration source is temperature compensated by a negative temperature coefficient (NTC) thermistor varying the bias voltage of the noise diode. The measured variation of the compensated calibration level is only ±0.5 K for 34 K calibration level at 1.4 GHz in a temperature range from −40°C to +40 °C. This internal noise calibration source is controlled by the detection of a tone signal applied on the RF output cable thus requiring no additional wiring to the amplifier. The designed noise calibration source provides monitoring of system noise temperature without the additional noise and cost of a directional coupler between ambient-temperature LNA and antenna.