Corticosteroids are effective for the treatment of many chronic and acute diseases but have many well-known adverse effects, which limit their use in some conditions. Steroid-induced psychosis is a rare side effect especially in the pediatric population. Although the estimated incidence of steroid-induced psychosis in adults is approximately 6%, it is rarely reported in the pediatric population. Moreover, it is poorly characterized and described in the literature. We report the case of a 4-year-old boy with no known medical or psychiatric history who presented to the emergency department with respiratory complaints. After observation and monitoring, the patient was diagnosed as having croup. A single dose of 8 mg dexamethasone was started intravenously. Within 3 h after the injection, the patient experienced psychiatric disturbances, including abnormal behaviors, anxiety, disorientation, decreased speech, and sleep disturbance. During the first 48 h of admission, the symptoms improved gradually, without using further medication during the rest of his hospital stay.