Mesalazine is a widely used and generally safe drug for the treatment of chronic inflammatory bowel diseases. Neutropenia/ Agranulocytosis rarely complicates this treatment and very few cases have been reported in the literature. Agranulocytosis is characterized by a decrease in peripheral neutrophil count to less 500 /mm3. Most reported cases presented more than three months after the initiation of treatment, and whilst many patients recovered, fatalities were reported. Cessation of mesalazine alone may not be adequate therapy and aggressive management with bone marrow evaluation, high dose of granulocyte colony-stimulating factor, or immunosuppressive therapy may be indicated. We report here the case of a patient with ulcerative colitis who developed an asymptomatic agranulocytosis during treatment with mesalazine and having spontaneously regressed after stopping treatment.