Background: In 2017, diphtheria outbreaks occurred in several provinces in Indonesia. In North Sumatra, data on diphtheria cases are rarely published. Therefore, information is needed to assess the clinical and laboratory characteristics that are associated with an increase in mortality of diphtheria. This study aims to determine the clinical dan laboratory profile of children with Diphtheria Methods: Retrospective cohort study to assess the association of clinical and laboratory characteristics with mortality. Research data was obtained from medical records of patients aged 1-18 years diagnosed with diphtheria clinically at H. Adam Malik Hospital Medan in the period January 2020 to December 2023. Results: The majority of children with diphtheria were male (56,8%) and the mean age of 8,14. Most patients did not receive any immunization for diphtheria (54,1%). During this period, the mortality rate was 16,2%. All participants experienced fever and sore throat. Pseudo-membrane was found in 36 cases (97.3%) followed by bullneck appearance (73%) and myocarditis (45,9%). Leukocytosis was found in 78,4% of cases while positive bacterial culture and thrombocytopenia were found in 59.5% and 51.4% of the cases Conclusions: The clinical profile of Diphtheria at Haji Adam Malik Hospital Medan showed that all cases with fever and sore throat, most of cases had pseudo-membrane, bullneck, and myocarditis. Leukocytosis, bacterial culture and thrombocytopenia showed over half of the cases.