A 61-year-old man with a 32-year occupational history of welding developed malaise, cough, and dyspnea after inhalation of smoke while welding galvanized steel. On admission, peripheral leukocytosis, hypoxemia, and diffuse granular and linear opacities on a chest X-ray were present. The bronchioli were exaggerated in a chest high-resolution CT. Bronchoalveolar lavage revealed mild lymphocytosis and transbronchial lung biopsy showed siderosis and exudation of fibrin and neutrophils into alveolar spaces. The clinical and radiographic findings later improved except for an obstructive disorder on pulmonary function test. The respiratory health hazards associated with welding vary according to the materials and the concentration of inhaled substances. Acute chemical pneumonitis caused by inhalation of zinc fumes (zinc oxide) was accompanied by chronic siderosis in this case. It is well known that metal fume fever commonly occurs when inhaling zinc oxide fumes. However, acute chemical pneumonitis after exposure to zinc oxide during welding has been only rarely reported.