With the advent of GaN as the major material system in the solid-state lighting industry—high power, high brightness LEDs with wavelength ranging from near UV to white are getting fabricated and part of a tremendously large and ever-increasing market. However, device self-heating and environment temperature significantly deteriorates the LED’s optical performance. Hence, it is extremely important to quantify the device self-heating and its impact on optical performance. In this work, three different characterization techniques were used to calculate temperature rise due to self-heating for an InGaN/GaN LED with 5 pairs of multiple quantum wells. The impact of self-heating and increased environment temperature on the device optical performance were also studied. Nanoparticle assisted Raman thermometry was used for the first time to measure the LED mesa surface temperature. The temperature measured using this technique was compared with temperature data obtained by using the forward voltage method and infrared (IR) thermography. The IR and Raman measurement results were in close agreement while the temperature data obtained from forward voltage method underestimated the temperature by 5-10%. It was also observed that due to environment temperature increase from 25ºC to 100ºC, LED optical power output drops by 12%.