Propylthiouracil (PTU) is commonly used to treat hyperthyroidism. However, it is associated with a number of adverse events. Especially, pulmonary complications, although rare, can be serious. Therefore, early detection is paramount. Here, we describe a first case of PTU-induced bronchiolitis obliterans organizing pneumonia (BOOP) pathologically confirmed by a surgical lung biopsy. Particularly, the present case shows that early detection coupled with withdrawal of PTU can lead to the resolution of symptoms and radiographic abnormalities without the need for corticosteroids. Although rare, PTU-induced BOOP should be considered in the differential diagnosis of pulmonary opacities in patients receiving PTU therapy.