This research aimed to determine the effectiveness of Dunaliella salina extract in reducing the damage of the cantang grouper brain, eyes and intestines tissue infected with VNN. Fifty seeds of cantang grouper were stocked into 5 pieces of 50 L volumes with a density of 10 fish/container. Before being infected with VNN, the groupers were treated with feed containing D. salina extract with a dose: K- (0 mg/kg feed), A (250 mg/kg feed) , B (300 mg/kg feed), C (350 mg/kg feed) and D (400 mg/kg feed) for 10 days. After 10 days of treatment, cantang groupers were injected by VNN through intramuscular injection with a dose of 0,2 ml/fish with concentration 104. Based on the research, D. salina extract which mixed into feed was effective in reducing the percentage of histopathological damage in the brain, eyes and intestines tissue of cantang groupers infected with VNN. The histopathological damaged tissue was necrosis, vacuolation, inclusion body, congestion, and goblet cell. The results showed that the lowest damage in the brain, eyes and intestine were found in treatment D (400 mg/kg of feed) with a percentage of damage 6,8%, 7% and 12,8%.