Systems and methods for measuring ambient and laser temperature in heat assisted magnetic recording (HAMR) systems are provided. One such system includes a slider having a write head, a laser diode coupled to the slider and configured to direct energy to a magnetic medium, and a preamplifier circuit including a voltage measurement circuit configured to measure a voltage drop across the laser diode, and a current measurement circuit configured to measure a current through the laser diode, where the preamplifier circuit is configured to store calibration information including a plurality of temperatures corresponding with measurements of the voltage drop across the laser diode and measurements of the current through the laser diode, and calculate a temperature based on the measured voltage drop across the laser diode, the measured current through the laser diode, and the calibration information.