Gastrointestinal bleeding is a critical abdominal emergency that frequently leads to hospital admission. While 80–85% of gastrointestinal bleeding cases may resolve on their own, they can escalate into severe haemorrhage and potentially fatal outcomes. The clinical manifestation of gastrointestinal bleeding varies widely: patients may be asymptomatic or mildly affected and may need only conservative management, or they may be critically ill and require urgent medical intervention. The challenge in identifying the source of bleeding lies in its diverse possible aetiologies, the extensive nature of the gastrointestinal tract, and the sporadic occurrence of the bleeding. The approach to diagnosis and treatment hinges on the specific characteristics of the bleeding and the patient’s haemodynamic condition. Radiologists must be knowledgeable about the strategic application of computed tomography angiography and other imaging techniques in the context of acute gastrointestinal bleeding. Additionally, they must understand both the indicators of bleeding and the potential for misdiagnosis to ensure accurate diagnosis and effective patient care. This chapter details the methodology of computed tomography angiography, including the advantageous applications of dual-energy computed tomography angiography, while offering practical advice and insights for recognizing both typical and atypical signs of acute gastrointestinal bleeding and pitfalls.