The purpose of this study was to describe the clinical, radiographic, and computed tomographic findings in dogs and cats with migrating intrathoracic grass awns. Thirty-five dogs and five cats with visual confirmation of a grass awn following surgery, endoscopy or necropsy, and histology were assessed. The medical records and all diagnostic imaging studies were reviewed retrospectively. Labrador Retrievers or English Pointers <5 years of age, with a history of coughing and hyperthermia, were the most common presentations. Seventeen animals had an inflammatory leukogram of which 14 had a left shift or toxic neutrophils. Radiographs were performed in 38 animals and computed tomography (CT) in 14. Thoracic radiographs were characterized by focal pulmonary interstitial to alveolar opacities (n=26) that occurred most commonly in the caudal (n=19) or accessory lobes (n=8). Additional findings included pneumothorax (n=9), pleural effusion (n=8), and pleural thickening (n=7). Pulmonary opacities identified on radiographs correlated to areas of pneumonia and foreign body location. CT findings included focal interstitial to alveolar pulmonary opacities (n=12) most commonly in the right caudal lung lobe (n=9), pleural thickening (n=11), mildly enlarged intrathoracic lymph nodes (n=10), soft tissue tracking (n=7) with enhancing margins (n=4), pneumothorax (n=6), pleural effusion (n=4), and foreign body visualization (n=4). Histologic diagnoses included pulmonary and mediastinal granulomas or abscesses, bronchopneumonia, and pleuritis. Migrating intrathoracic grass awns should be considered as a differential diagnosis in coughing, febrile animals with focal interstitial to alveolar pulmonary opacities, pleural effusion, pleural thickening, and/or pneumothorax on radiographs or CT.