ZnO particles were synthesized by hydrothermal route at 95 °C, with different ethylammonium nitrate (EAN):water volume ratio (0.01 to 1) in reaction media. Morphology of ZnO particles changed from initial cylindrical to intermediate spindle and finally to spherical with increasing concentration of EAN in reaction media whereas pH of aliquots remained within range of 7–7.5. Aggregates of EAN bind to Zn2+ enriched both terminal planes as well as to Zn2+ and O2− enriched side planes of basis units which finally resulted to formation of spherical ZnO superstructures. Favorable H-bond and electrostatic interaction helped to bind EAN aggregates with surfaces of ZnO crystals. It was found that the spherical ZnO superstructures showed novel photoluminescent property and enhanced photocatalytic activity compared to that of the commercially available ZnO.