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The contributing factors that determine the reliability characteristics of GaN-based white light-emitting diodes (WLEDs) with dual degradation kinetics were investigated. For this study, an aging test of WLEDs was performed at temperatures of 60 °C, 80 °C, and 100 °C under a constant dc of 300 mA. Evidence for dual degradation kinetics could be observed by the optical output degradation occurring with the modification of chromatic properties (due to the deterioration of packaging materials) and the evolution of leakage currents (due to the generation of nonradiative defects). By comparing temperature-dependent output degradation with the modification of chromatic properties or the evolution of leakage currents, the contributing factor that predominantly determines the reliability characteristics was estimated, i.e., the contributing factor for generated nonradiative defects versus the degraded packaging materials was 75:25 at 60 °C and 32:68 at 100 °C. This indicates that the predominant degradation kinetics change as the aging temperature varies. The activation energy of WLEDs was shown to be as low as 0.33 eV using Arrhenius plots of half-lifetime, which is attributed to the dual degradation kinetics.