Although drug-induced interstitial pneumonitis caused by gefitinib is well recognized in Japan, reports of alveolar hemorrhage caused by gefitinib are very rare. We encountered a case of alveolar hemorrhage thought to be caused by gefitinib. A 74-year-old woman with non-small cell lung cancer (adenocarcinoma; cT4NOM0, stage IIIB) had been receiving gefitinib as second-line therapy from January 2009. However, bloody sputum and nasal bleeding were observed 2 weeks after the initiation of gefitinib therapy. Chest radiography and computed tomography revealed ground-glass opacities predominantly in the lower lung fields. Bronchoscopy was performed, and the bronchoalveolar lavage fluid obtained from the right B8 was bloody. Her symptoms and chest ground-glass opacities improved after the withdrawal of gefitinib. Based on these clinical findings, we diagnosed alveolar hemorrhage caused by gefitinib. If chest radiography or computed tomography findings of gefitinib-treated patients show ground-glass opacities, the possibility of not only interstitial pneumonitis, but also alveolar hemorrhage should be considered in the differential diagnosis.