A 47-year-old man was admitted to our hospital with complaints of chronic cough and chest radiographic abnormality. Chest computed tomography (CT) showed bilateral diffuse centrilobular nodules. Transbronchial lung biopsy specimens showed nonspecific findings. Since the chest CT findings worsened six months later, a video-assisted thoracoscopic lung biopsy was performed for diagnosis. Histological findings showed a variety of foreign body granulomas around bronchioles, which suggested aspiration. We diagnosed him as diffuse aspiration bronchiolitis (DAB). His swallowing function was normal on fiberoptic endoscopic evaluation. A detailed history taking revealed that he often took sleeping pills with alcohol and vomited while sleeping. Hiatal hernia was detected by upper gastrointestinal endoscopy. Gastroesophageal reflux disease was suspected to cause DAB. After he had permanently stopped drinking alcohol, the nocturnal vomiting almost disappeared and chest CT findings improved. DAB should be recognized as a differential diagnosis in patients with diffuse nodular shadows on chest CT, and detailed history concerning aspiration, including GERD, should be taken even in the case of nonelderly population.