Nontraumatic abdominal wall and peritoneal emergencies comprise a spectrum of conditions ranging from those that are self-limiting and managed conservatively, to others that are potentially life-threatening and require immediate, multi-specialty levels of care and intervention. Imaging, particularly computed tomography (CT), plays an essential role in the care of patients with a suspected nontraumatic abdominal wall or peritoneal emergency. Nontraumatic emergencies of the abdominal wall include complications associated with hernias, abdominal wall fluid collections, and soft-tissue necrotizing infections (fasciitis); fistulas from the gut to the abdominal wall; rectus sheath hematomas; and complications associated with indwelling medical devices or catheters. Nontraumatic peritoneal emergencies include peritonitis, hemoperitoneum, pneumoperitoneum, peritoneal carcinomatosis, epiploic appendagitis, omental infarction, mesenteric adenitis, and mesenteric panniculitis. The emergency radiologist must be familiar with the imaging appearance of abdominal wall and peritoneal emergencies, to help guide clinical management of these patients by establishing a diagnosis and identifying any potential complications.