A 51-year-old Japanese man was admitted to our hospital with the complaint of exertional dyspnea. A diagnosis of chronic idiopathic interstitial pneumonia (C-IIP) was made on the basis of findings of hypoxemia, restrictive ventilatory impairment, and interstitial shadows disclosed by chest roentgenograms. Chest computed tomographic (CT) scans clearly demonstrated left-side dominance of fibrotic changes. Dynamic CT and magnetic resonance angiography revealed the presence of thrombi in the left pulmonary artery. Lung scintigrams showed mismatching between ventilation and perfusion in the left lung. Pulmonary arteriography confirmed the diagnosis of left pulmonary thromboembolism (PTE). This was a rare case of PTE and C-IIP in which fibrotic changes occurred predominantly in the left lung field.