Background: Necrotizing enterocolitis (NEC) is a serious complication of prematurity. Currently, there is limited evidence to guide investigation and treatment strategies. Objectives: To evaluate the parameters used to diagnose or exclude NEC, and to identify differences between neonatologists and pediatric surgeons. Methods: A scenario-based survey was sent to neonatologists and pediatric surgeons. Results: 173 physicians from 26 countries completed the survey (55% neonatologists and 45% pediatric surgeons). Bloody stools, abdominal tenderness, low platelet counts, and increased lactate levels increased the likelihood of NEC for 82, 72, 56, and 45% of respondents, respectively. Intestinal pneumatosis, portal venous gas, and pneumoperitoneum on X-ray increased the likelihood of NEC for 99, 98, and 92% of respondents, respectively. Clinical examination and laboratory tests were insufficient to exclude NEC, but normal intestinal movements and normal gut wall thickness on ultrasonography decreased the likelihood of NEC for 38 and 33% of respondents, respectively. Neonatologists more frequently relied on increased gastric residuals and abdominal distension to diagnose NEC (p = 0.04 and p = 0.03, respectively), whereas pediatric surgeons more frequently reported that absence of bloody stools helped to exclude NEC (p = 0.04). In a deteriorating patient with suspected NEC, 39% of respondents would broaden the antibiotic spectrum, and 42% would recommend a laparotomy. Conclusion: Our results indicate a wide variation in the management of NEC, with significant differences between neonatologists and pediatric surgeons. A better appreciation of the relative significance and weighting that should be applied to the clinical features and investigations should reduce the variation in interpretation that appears to exist.