Pristine and amine functionalized ZnO nanoflakesbased fiber-optic sensors were investigated towards different volatile compounds (VCs) for environmental monitoring applications. The ZnO nanoflakes synthesized through co-precipitation method was subjected to X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectrometer, and optical absorption studies to examine the structural, morphological, elemental, and optical properties. The analysis confirms the formation of ZnO nanoflakes with wurtzite structure. The spectral response of the ZnO and amine functionalized ZnO nanoflakes-based fiber-optic gas sensors were studied at ambient temperature for various concentrations (0C300 ppm) of acetone, ammonia, ethanol, methanol, hexane, and chloroform in clad modification technology. The analysis revealed that the pristine ZnO nanoflakes have selectivity towards acetone and amine functionalized nanoflakes have enhanced sensitivity towards all VCs and high selectivity (∼ four times) toward ammonia with fast response and recovery. Further, the pristine ZnO-based sensor shows selectivity towards acetone above 150 ppm with the response and recovery time of 19 s and 23 s, whereas the sensor based on amine functionalized ZnO shows enhanced selectivity towards ammonia above 50 ppm with fast response and recovery time of 14 s and 17 s, respectively. © 2017 IEEE.