A 39-year-old woman was referred to our hospital after incidental detection of a hypoechoic abdominal mass on ultrasonography at the 11th week of gestation. Magnetic resonance imaging confirmed a 20 cm cystic lesion just cephalad to the left kidney. The patient delivered in the 40th week of gestation without complications. After 3 years of follow-up, she presented with acute left flank pain. Physical examination revealed pale palpebral conjunctiva and abdominal fullness. Contrast-enhanced computed tomography confirmed a 21 × 17 × 15 cm hemorrhagic cyst arising from the left adrenal gland. Laparoscopic left adrenalectomy was performed. Pathological examination revealed a vascular cyst (endothelial cyst) of the adrenal gland. Surgical intervention is indicated for large adrenal cysts which may cause bleeding into the cavity.