InGaN/GaN light-emitting diodes ͑LEDs͒ with graded-thickness multiple quantum wells ͑GQW͒ was designed and grown by metal-organic chemical vapor deposition. The GQW structure, in which the well-thickness increases along ͓0001͔ direction, was found to have superior hole distribution as well as radiative recombination distribution by performing simulation modeling. Accordingly, the experimental investigation of electroluminescence spectrum reveals additional emission from the narrower wells within GQWs. Consequently, the efficiency droop can be alleviated to be about 16% from maximum at current density of 30 to 200 A / cm 2 , which is much smaller than that for conventional LED ͑32%͒. Moreover, the light output power was enhanced from 18.0 to 24.3 mW at 20 A / cm 2 .