Retroperitoneal hematoma is an uncommon clinical entity that may be encountered more frequently as iatrogenic injuries occur during interventional procedures. This chapter presents a case study of a 71-year-old male who presented to the emergency room with new onset headache, stiff neck, and slight confusion. The clinical manifestations of retroperitoneal hematoma are vague and thus the clinician must have a high index of suspicion to make the diagnosis. If the hematoma develops near or within the iliopsoas muscle, patients will present with a femoral neuropathy. Diagnosis of retroperitoneal hematoma is made either via computed tomography (CT) or angiography. However, if the patient is unstable or has ongoing bleeding, endovascular therapy with stent-grafting across the injured vessel is a treatment option if interventional radiology is available. Surgery may also be indicated to decompress the retroperitoneal space if nerve or ureteral compression exists.