Background and Aim: Respiratory distress is one of the most common underlying causes of Emergency Department visits in children, with a high morbidity and mortality rate which could raise a lot of concerns, acquiring early recognition of the underlying cause and appropriate treatment. The current study aimed to determine the prevalence and distribution of underlying causes of respiratory distress. Material and Methods: In this retrospective cohort study, demographic and clinical information of 154 patients older than one month who were referred to the Mofid Children’s Hospital emergency department in Tehran, Iran, from October 2018 to April 2019 were gathered from Hospital Information System (HIS) and analyzed with SPSS Statistics 23.0 version. Results: 154 participants were recruited with a mean age of 33.02±37.21 months, and 66% were male. The most common clinical symptom among these children was tachypnea (90.6%). Asthma (35.1%), pneumonia (31.8%), sepsis (8.4%), bronchiolitis and croup (7.8%), and foreign body (7.1%) were the most common causes of respiratory distress. When comparing clinical symptoms, nasal flaring was substantially more common in younger individuals than in older patients (P-value=0.04), but there were no significant differences between the sexes. In terms of underlying causes, patients with bronchiolitis and airway malformation were considerably younger than those without these disorders (P-value 0.001), whereas patients with chest wall deformity were more likely to be older (P-value=0.01), and it was more frequent among girls (P-value=0.03). Conclusion: Respiratory distress can be manifested with a variety of signs and symptoms and different underlying causes which may defer in different genders, ages, and regions. Among patients referred to a tertiary center in Tehran, tachypnea was the most common clinical symptom, and asthma was the most frequent cause of respiratory distress. Knowing the underlying causes of this emergent clinical status in pediatrics can help us in developing appropriate treatment approach.