Background: Portal hypertension (PH) refers to a clinical syndrome characterized by an elevation in the pressure gradient between the portal and hepatic veins. It is necessary to identify the underlying causes to manage this disorder effectively. Objectives: This study aimed to investigate the etiology, clinical manifestations, and endoscopic findings in children with PH. Methods: This analytic cross - sectional study was performed on patients (< 18 years) with PH who were referred to the Pediatric Gastroenterology Clinic of Mofid Children’s Hospital in Tehran, Iran, within 2014 - 2020. The demographic details of the patients were collected from their medical records. Clinical manifestations, age at diagnosis, family history, and endoscopic findings were also recorded. Results: A total of 102 patients participated in this study. The subjects’ mean age was 6.81 ± 4.46 years. The results revealed that 50 (49.0%) and 46 (45%) cases had PH due to extrahepatic and intrahepatic diseases, respectively. Autoimmune hepatitis and portal vein thrombosis were the most common etiology of intrahepatic and extrahepatic PH, respectively. Based on the endoscopic analysis, esophageal varices were the most common findings (95.8%) observed in patients with PH. Conclusions: Extrahepatic diseases were the most prevalent PH etiology in children referred to the Pediatric Gastroenterology Clinic of Mofid Children’s Hospital.