Serous effusions have been most commonly associated with ascites, pericardial effusion, and heart failure. But, they have been considered to be an unusual form of complication in hypothyroidism and pleural effusion, which has been observed as an isolated finding in hypothyroidism is apparently rare and complete analysis of these types of hypothyroid-associated pleural effusions has yet not been described. We report a case of hypothyroidism associated with unilateral pleural effusion in a 77 year-old male patient who was improved through levothyroxine sodium with brief review of the literature.