A detailed knowledge of the temperature profile is critical in many microelectromechanical systems (MEMS) devices. We used fluorescent microthermal (FMT) imaging for measuring this profile in a MEMS microheater that is an integral part of a glucose-sensing chip. The temperature profile on the heater surface was measured for a range of applied powers below 1 mW. The maximum temperature at the heater center was found to vary linearly with the applied power from room temperature to similar to 50 degrees C. The imaging was sensitive to temperature changes on the order of 0.1 degrees C. Finite element modeling confirmed both the two-dimensional profile of the temperature on the heater surface as well as the dependence of the temperature on the applied power.