We report, a shape controlled novel synthesis of Indium oxide (In2O3) nanocapsule using biogenic reflux method. The In2O3 samples were obtained through optimization of the concentration of sodium citrate, which played a significant role to tune the size of nanocapsules. All synthesized In(2)O(3 )samples were characterized by using X-ray diffraction (XRD), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The morphological study reflects the effect of sodium citrate on the size of nanocapsules and confirms the formation of nanocapsules in the range of 50 nm. Furthermore, the photocatalytic activity of In(2)O(3 )nanocapsules based photocatalyst was carried out for the degradation of Crystal Violet (CV) dye under natural sunlight illumination. The experiment revealed that the In(2)O(3 )nanocapsule efficiently degrades 90% of CV within 180 min. This effort recommends the synthesis of In(2)O(3)nanocapsule based photocatalyst for rapid degradation of CV under natural sunlight illumination. (C) 2019 Elsevier Inc. All rights reserved.