Spontaneous splenic rupture (SSR) is a rare but potentially life-threatening entity. It can be due to neoplastic, infectious, haematological, inflammatory and metabolic causes. An iatrogenic or an idiopathic aetiology should also be considered. Depending on the degree of splenic injury and the haemodynamic status of the patient, it can be managed conservatively. A 61-year-old man presented to the emergency department with an acute abdomen, hypovolaemic shock and clotting abnormalities. However, his focused assessment with sonography for trauma showed no evidence of an aortic aneurysm, rupture or dissection. Further investigation with a CT angiogram aorta confirmed a subcapsular splenic haematoma with free fluid in the pelvis and a mass in the superior pole of the spleen. He was diagnosed with an SSR. He was initially managed non-operatively. However, his repeat CT showed an enlarging haematoma and he underwent embolisation of his splenic artery. Ultrasound-guided core biopsy of his splenic mass confirmed the diagnosis of diffuse large B-cell lymphoma. This paper will discuss the clinical presentation, differential diagnosis and management of SSR. Furthermore, it provides an important clinical lesson to maintain a high index of clinical suspicion for splenic injury in patients presenting with left upper quadrant abdominal pain radiating to the shoulder. This case also reinforces the importance of close observation and monitoring of those individuals treated conservatively for signs of clinical deterioration.