Gemcitabine is widely accepted as the standard treatment for pancreatic cancer, but it can cause unpredictable side effects. Acute respiratory distress syndrome is a rare complication with gemcitabine, but is sometimes fatal. We describe a cured case of acute, severe gemcitabine-induced pulmonary toxicity. The patient was a 76-year-old man with pancreatic cancer who was receiving adjuvant gemcitabine chemotherapy after surgery. The patient received gemcitabine 1,000 mg/m2 on days 1, 8, and 15 for three 4-week cycles, with intervals of 1 week. He developed severe general fatigue on day 1 of the third cycle. Computed tomography showed diffuse ground-glass opacity with pleural effusion. There was no increase in β-D-glucan, and cytomegalovirus antigenemia assays were negative. No bacteria or acid-fast bacilli were found. The number of eosinophils in bronchoalveolar lavage fluid was increased. Considering these data, we diagnosed eosinophilic pneumonia induced by gemcitabine. The patient was immediately treated with a steroid and neutrophil elastase inhibitor under respiratory supportive therapy. After 4 weeks, his pulmonary symptoms were markedly improved. Physicians should be cognizant of the possible association of serious pulmonary toxicity with gemcitabine treatment. A delay in diagnosis and treatment could lead to a fatal outcome.