Objective This study aims to examine the impact of age at first diagnosis on the prognosis of hepatoblastoma (HB) in children, providing evidence to improve the risk stratification of HB. Methods Data from 403 cases of HB diagnosed at the First Affiliated Hospital of Sun Yat-sen University between February 2010 and September 2023 were collected. Kaplan-Meier survival analysis, COX regression analysis, and binary logistic regression were employed for statistical analysis. Results The hazard ratio (HR) for event-free survival (EFS) reduction in HB patients was 1, 0.862, 1.393, 2.008, 1.325, 1.859, 3.667 (P=0.001), and 2.502 (P=0.023) for first diagnosis ages of 0-1, 1-2, 2-3, 3-4, 4-5, 5-6, 6-8, and ≥8 years, respectively, the HR for overall survival (OS) was 1, 0.410, 0.876, 1.713, 1.243, 0.575, 3.012 (P=0.039), and 2.012, respectively. After adjusting for newly diagnosed alpha-fetoprotein (AFP), pre-treatment extent of tumor (PRETEXT) stage, and PRETEXT stage annotation factors, the prognosis of HB for patients diagnosed at ≥6 years old and <6 years old remained statistically different. There was no statistical difference in HR for EFS and OS reduction among the 0-1 month, 1-3 month, 4-6 month, 7-9 month, and 9-12 month groups. Conclusion Being diagnosed at age ≥6 years is an independent risk factor for poor prognosis in HB. Age has no effect on the prognosis of HB during infancy.