Methotrexate is commonly used in rheumatoid arthritis as an anti-inflammatory agent, but treatment with methotrexate can lead to severe side effects, especially pulmonary complication. Interstitial pneumonitis is one of the most important pulmonary adverse effects of methotrexate and most patient present with a subacute febrile illness and peripheral eosinophilia is seen in about a half of patients. Almost all patients have abnormal chest roentgenograms and bibasilar interstitial infiltration with alveolar pulmonary consolidations is the most characteristic finding. Interstitial inflammation with mononuclear cell infiltration is a characteristic pathologic feature and findings that suggest acute hypersensitivity pneumonitis, such as bronchiolitis, granuloma formation with giant cells, and infiltration with eosinophils are often present. Methotrexate-induced pneumonitis is a potentially life threatening and unpredictable complication but it is difficult to make a definite diagnosis in the absence of high index of clinical suspicion. Early recognition and appropriate management may avoid the serious outcome. Herein we report a case of methotrexate-induced pneumonitis in a patient with rheumatoid arthritis.