Adrenal cysts are rare and are usually discovered incidentally during diagnostic imaging, surgery, or autopsy. Most cystic lesions of the adrenal gland are nonfunctioning and become symptomatic when complicated by rupture, hemorrhage, or infection. A 40-year-old woman presented with a history of gradual-onset pain in her left flank region at 20 weeks' gestation. Ultrasound showed a 20-cm cystic mass in her left abdominal cavity. Pertinent laboratory tests were within normal limits. The patient underwent exploratory laparotomy, which revealed a 20 x 15-cm left adrenal cyst; thus, we performed left adrenalectomy with complete excision of the cyst. Histological examination confirmed a hemorrhagic adrenal pseudocyst. The patient had an uneventful postoperative course, and subsequent routine obstetric ultrasound examinations showed normal fetal activity and development until the pregnancy terminated with a stillbirth caused by pre-eclampsia at 34 weeks' gestation. To the best of our knowledge, this is only the 12th reported case of adrenal pseudocyst discovered during pregnancy. We analyze the clinicopathologic findings and discuss the possible association of pregnancy, with special reference to etiopathogenesis, presentation, diagnosis, and treatment.