Adrenal ganglioneuromas are rare tumors arising from sympathetic ganglion cells that may present similarly to other adrenal tumors, making preoperative diagnosis challenging. We present a case of a young woman with a history of Hashimoto's thyroiditis who presented with hypertension and headaches. An abdominal CT scan revealed a large left adrenal mass, and while laboratory tests for catecholamines and metanephrines were normal, the suspicion for pheochromocytoma remained high given the size of the mass and persistent hypertension. The patient was started on alpha-blockers and beta-blockers in preparation for surgical removal. Pathology revealed a mature ganglioneuroma without evidence of malignancy, and postoperative blood pressure was normalized. We hypothesize that vessel compression from the large mass created functional stenosis, resulting in persistent hypertension. This case highlights the importance of a thorough workup for hypertension in young adults and routine preventative care visits to avoid delayed management. Adrenalectomy with histopathological examination remains the gold standard for treatment and diagnosis, and patients have a good prognosis following resection, with minimal need for recurrent therapy.