Diisononyl phthalate (DINP) is used as a plasticizer for PVC products. Freshwater fish, Oreochromis mossambicus were exposed to DINP at 300 ppm concentration for 24, 48, 72 and 96 h maintaining positive (propylene glycol as solvent) and negative (without solvent and toxicant) control groups. At the end of every treatment period, gill, liver, muscle and ovary were dissected and fixed in buffered formalin. Histopathological changes in gill includes epithelial lifting, hyperplasia, aneurysm, blood vessel dialation, lose of primary and secondary lamellae. DINP-induced hepatic damages like cytoplasmic vacuolization, spindle shaped nuclei and necrosis was observed. Muscle tissues undergone various types of damages such as thickening of muscle bundle, segmented muscle fibres and muscular dystrophy. Histopathological modifications in ovary were observed as progressive reduction in the number of matured oocytes, increase in distorted and atretic oocytes. The present study demonstrates that acute exposure to DINP alters the normal architecture of vital tissues in fish.