Azacitidine is a pyrimidine nucleoside analog licensed for treatment of adult patients with myelodysplastic syndrome. Azacitidine acts as an inducer of cell differentiation by causing demethylation and re-expression of genes silenced by hypermethylation. We report a 56-year-old man with myelodysplastic syndrome who developed interstitial lung disease after azacitidine therapy. Open lung biopsy revealed a nonresolving organizing pneumonia pattern and bronchocentric granulomatous pattern suggestive of drug-induced lung injury. Treatment with steroids and discontinuation of azacitidine led to resolution of interstitial lung disease. The Naranjo adverse drug reaction probability scale score indicated that the association between azacitidine and interstitial lung disease was probable. Interstitial lung disease is a serious but uncommon side effect of this relatively safe drug. The mechanism underlying this is still unclear. The patient was subsequently treated with decitabine with no recurrence of interstitial lung disease.