Type 1 diabetes is characterized by insulin deficiency due to destruction of pancreatic beta-cells. A novel subtype of type 1B which is rapidly developed without any evidence of autoimmunity has been recently proposed as fulminant type I diabetes. In female patients of child-bearing age, the onset of fulminant type 1 diabetes occurred frequently during pregnancy or after delivery in Japan, however, there was no report about fulminant type 1 diabetes associated with pregnancy in Korea. We report a case of fulminant type 1 diabetes associated with pregnancy. A 28-year-old woman suffering from excessive thirst with vomiting and general weakness after four days from normal spontaneous vaginal delivery presented to our hospital. Laboratory examination revealed a high blood glucose level and evidence of diabetic ketoacidosis, butHbA1c level was normal. These findings suggested a very recent onset of diabetes mellitus. Serum C-peptide level was very low level. Antibodies to glutamic acid decarboxylase (GAD) was weakly positive. After fluid and insulin based management, patient successfully recovered without any serious complication.