Mesalazine-induced eosinophilic pneumonia has been rarely reported. We reported a case of mesalazine-induced eosinophilic pneumonia in a 56-year-old female who took mesalazine without a prescription for suspected ulcerative colitis. She had an elevated eosinophil count in peripheral blood and bronchoalveolar lavage fluid. Eosinophil infiltration was also noted in bone marrow aspirates. Chest radiograph and computed tomography demonstrated bilateral upper lung predominant infiltrates and spirometry showed a restrictive ventilatory defect with a reduced diffusion capacity. The patient recovered after cessation of mesalazine therapy. Mesalazine-induced lung damage should be considered in patients who develop unexplained respiratory symptoms while taking this agent.