The current study was conducted to investigate the histopathological toxic effect of Virkon at a concentration of 4 mg/L (therapeutic concentration) on the vital organs of common carp (Cyprinus carpio) fish. 120 common carp, with a mean weight of 230±10g, were distributed into eight glass aquariums (80cm 40cm 40cm) with their equipment (oxygen motor, water heater fixed at 25±1°C, thermometer). There were 15 fish in each aquarium, and they were randomly divided into four groups, with each group having duplicates. Group A (the control) was left untreated. Group B was continuously exposed to Virkon for 7 days. Group C was exposed to Virkon for 7 days, followed by a 3-day interval, and then a 7-day retreat with Virkon. Group D was exposed to Virkon for 14 days continuously. Tissue samples of the gill, liver, and kidney were collected on days 7, 14, and 21 of the experiment. The study revealed considerable effects of Virkon on the tissues, including hyperplasia of the primary lamella and the secondary lamella of the gill, along with hypertrophy of chloride cells. There was vaculative degeneration of hepatocytes with hemorrhage in hepatic tissue after 7 days of exposure, and the lesions became more intensive in group d with a longer exposure period. The kidney lesions showed vaculative degeneration of epithelial cells lining the renal tubules with hyaline casts in the renal tubules. The histopathological lesions became more exhaustive with a longer exposure period in all the studied organs, even with a short interval period