Current work confers mechanochemical and hydrothermal syntheses of ZnO, its characterization and photocatalytic applications. Mechanochemical and hydrothermal assisted syntheses of ZnO involve two stages viz. formation of precursors followed by its calcination. The suitable calcination temperature for precursor materials to get ZnO was obtained by TG-DTA and FT-IR Spectroscopic study; XRD data of these samples specified hexagonal wurtzite crystallite structures of ZnO. FESEM photographs of mechanochemically and hydrothermally synthesize ZnO confirmed nanocrystalline hexagonal granular and stacked block-like particle morphologies respectively. EDX spectra of these samples support their elemental purity. The UV-DRS study was used to measure the optical band gap of ZnO samples. Optical properties of ZnO samples were also studied with room temperature PL spectra. Photocatalytic applications of aforementioned ZnO samples were investigated with Xylenol Orange as a model organic dye. The PCD efficiency of ZnO was estimated in terms of percent degradation reference to various operating factors. KEYWORDS zinc oxide, Xylenol Orange, mechanochemical, hydrothermal, PCD efficiency ACKNOWLEDGEMENTS Authors are exclusively grateful to PDEA's Annasaheb Waghire College, Otur for providing their continuous and valuable support, in terms of amenities like laboratories for all experimental work and library for the literature review. Authors are also thankful to PDEA's Baburaoji Gholap College, Sangvi and CIF, SPPU, Pune for giving instrumental facilities for the characterization of materials. FOR CITATION Kaldante Y.D., Chaskar M.G. A comparative study of photocatalytic degradation of Xylenol Orange dye under natural sunlight over ZnO nanoparticles synthesized via mechanochemical and hydrothermal assistance routes.