Delirium is a syndrome with an acute onset that is accompanied by fluctuation and is associated with behaviors that indicate impaired consciousness and cognition. It is common and costly and is associated with severe functional decline and distress in an adult. However, its detection and diagnosis are so challenging in children. Herein, we report a 2-year-old girl who was admitted in the pediatric intensive care unit (PICU) with pneumonia and was intubated because of respiratory failure. She needed a lot of benzodiazepine and opioid drugs to be sedated. During hospital course after extubation, she developed by agitation and restlessness and dissociation from environment. Electroencephalography was done and diffuse generalized slow wave was observed. Finally, by environmental factors' correction, benzodiazepine decreasing, and risperidone administering, she became well and discharged. Delirium should be considered as an important, underdiagnosed, and common condition in the PICU. It should be considered in altered cognition, consciousness, and circadian rhythm disturbance situation in children.