Adrenal pseudocysts are rare lesions that are usually nonfunctioning and asymptomatic. We describe a patient who presented with nonspecific upper abdominal pain, vomiting, and hypertension. Ultrasonography and computed tomography revealed a giant left adrenal cyst. Routine laboratory tests and endocrine function tests were all normal. The patient underwent surgery, and the cyst was completely removed. Histologic examination showed that the cystic wall consisted of fibrous tissue without an epithelial or endothelial lining, and a diagnosis of an adrenal pseudocyst was made. Symptoms of pyloric obstruction resolved after pseudocyst removal. His blood pressure normalized and he was normotensive and symptom free 6 years after surgery.