Objective Carbon monoxide (CO) is a gas, which is produced by incomplete combustion of hydrocarbon-containing substances, and causes significant tissue and organ damage in the common event of CO poisoning. This study aims to evaluate the demographic, clinical, and laboratory characteristics of patients diagnosed with CO poisoning in the emergency department and to determine the factors associated with severe course in the acute phase of poisoning. Methods A total of 331 patients diagnosed with CO poisoning in Hacettepe University Children's Hospital, Pediatric Emergency Unit, between January 2004 and March 2014 were included in the study. Their demographic characteristics, presenting complaints, physical examination findings, Glasgow Coma Scale scores, carboxyhemoglobin, leukocyte, hemoglobin, troponin T, pH and lactate levels, type of treatment (normobaric or hyperbaric oxygen), intensive care unit admissions, and outcome of poisoning were investigated. Results Ninety-three patients were given hyperbaric oxygen. Fifty-one patients were admitted to the pediatric intensive care unit, 18 patients have had a severe clinical course, and 6 patients have died. The risk factors associated with severe disease course were determined to be low Glasgow Coma Scale score, high leukocyte count, and high troponin T levels at presentation. Conclusions Glasgow Coma Scale score, leukocyte count, and troponin T level may be beneficial in predicting clinical outcomes and tailoring therapy in children with CO poisoning.