Background <p>Spontaneous superior mesenteric artery (SMA) branch pseudoaneurysms are exceedingly rare and should be kept as a diagnosis in patients with trauma, pancreatitis, anticoagulant use or surgery presenting with unexplained abdominal pain, sudden drop in haemoglobin or hypovolemia. Computed Tomography Angiography (CTA) and Digital Subtraction Angiography (DSA) both readily demonstrate the vascular abnormality, with DSA being advantageous for therapeutic purposes. Computed Tomography (CT) of the abdomen frequently identifies haemoperitoneum or a localised hematoma at the site of a vascular abnormality. Embolisation with glue and coil is a safe and less invasive technique for successful endovascular repair.</p> Case Presentation <p>A male patient in the sixth decade of life presented with unexpected haemoperitoneum during laparotomy for radical cystectomy. After abandonment of the surgery, the patient underwent a CT abdomen revealing a pseudoaneurysm arising from the transverse pancreatic branch of the SMA, leading to retroperitoneal haematoma and haemoperitoneum, and subsequently underwent successful glue embolisation. Retrospectively evaluated CT abdomen done for preoperative evaluation in the recent past was normal.</p> Conclusions <p>This case report highlights SMA branch pseudoaneurysms presenting as unexplained haemoperitoneum and retroperitoneal haematoma in an asymptomatic patient, successfully treated by the endovascular route.</p>