This study focused on the importance of the interfacial adhesion in the zirconia (ZrO2)/silicone hybrids as the encapsulating material on the reliability of the LEDs. Surface-modified ZrO2 nanoparticles (m-ZrO2) with functional groups were prepared by a sol-gel reaction which could become reactive to the silicone resin. The produced m-ZrO2/silicone hybrid at 5 wt% had a refractive index of 1.569 at 633 nm and light transmittance of 98.9%. Moreover, the coefficient of thermal expansion was greatly reduced by the introduction of m-ZrO2 into the silicone resin. When using this m-ZrO2/silicone hybrid, the luminous flux of the LED was 10.1% higher than that using a neat silicone resin. Most importantly, the LEDs encapsulated with the m-ZrO2/silicone had the best performance under thermal shock among all the LEDs tested in this study, owing to its strong interfacial adhesion between the nanoparticles and matrix. Moreover, the thermal stresses developed in hybrids were calculated and found to agree with the performance evaluation of the encapsulated LEDs under thermal shock, in which the m-ZrO2/silicone hybrid had the lowest thermal stress. This study proposed that the m-ZrO2/silicone hybrid material with strong interfacial adhesion could be useful for the encapsulation of LEDs even under extreme thermal conditions. (C) 2017 Elsevier B.V. All rights reserved.