Thoracic actinomycosis represents about one-fourth of all cases of the disease. Isolated pleural effusion due to Actinomycosis is rare. We report a case of right sided pleural effusion with discharging sinus in the right anterior chest wall. Actinomycosis was suspected and confirmed by microscopic identification of "sulfur granules" in the discharge of the sinus tract and also identification of gram-positive filamentous bacteria in the specimen of discharging sinus. The patient improved clinically and radiologically after treatment with intravenous penicillin G followed by oral penicillin and aspiration of pleural fluid.