Background: Children in neonatal intensive care units (ICU) are more susceptible to medical errors. Measuring adverse events is a very important issue for patient safety and using trigger tool methodology as a different strategy is beneficial to both more focused as well as rapid chart review to establish whether or not an adverse event occurred. Aim: For evaluation the prevalence of adverse events (AEs) in Mit-Ghamr Neonatal ICU using the trigger tool and to evaluate the prevalence of adverse events in Mit-Ghamr neonatal Intensive Care Unit with other hospitals in Egypt and abroad. Subjects and Methods: A cross sectional analytic study using medical record review and charts study was done including 511 medical records, it consisted of all neonates admitted to Mit-Ghamr neonatal ICU between 1^st January to 31 December 2017. Results: a total of 465 adverse events with incidence rate of 0.91 adverse event/patient and 1.16 trigger/patient. The most common adverse event was nosocomial infections with more than half of the overall adverse events (n=282; 55.2%), followed by catheter infiltration (n=64; 12.5%), hypotension was 5.5%, respiratory arrest 4.7%, accidental extubation 4.1%, death 3.5%, renal insufficiency 2%, and seizures was 0.6%. Category (F) was the most prevalent harm category among the occurred adverse events (45.7%) followed by category (E) (28.8%). Only a minority (3.1%) had a permanent harm (category G) and category H was 22.4%. Conclusion: Nosocomial infections constitute the majority of all adverse events, followed by catheter infiltration and hypotension.