The pediatric population has a number of unique considerations related to the diagnosis and treatment of ascites. This review summarizes the physiologic mechanisms for cirrhotic and noncirrhotic ascites and provides a comprehensive list of reported etiologies stratified by the patient's age. Characteristic findings on physical examination, diagnostic imaging, and abdominal paracentesis are also reviewed, with particular attention to those aspects that are unique to children. Medical and surgical treatments of ascites are discussed. Both prompt diagnosis and appropriate management of ascites are required to avoid associated morbidity and mortality.