Aim: Sarcopenia is associated with poor prognosis in adult oncologic patients, with little evidence of this association in pediatric population, including hepatoblastoma. Methods: Retrospective study in patients with hepatoblastoma, divided into those with or without sarcopenia. Sarcopenia was assessed by measuring psoas muscle area (PMA) at L4-L5 level on the CT/MR and defined as z-score values ≤2. Relapse and mortality were analyzed. Results: Twenty-one patients (57.1% male) were included, with median age 35.7 months (IQR: 23.5-58.5). Seven (33.3%) had sarcopenia on initial studies compared to 14 (66.7%) who did not. No differences were found between groups in age, weight, PRETEX, surgical treatment or a-fetoprotein levels. Twelve (57.1%) underwent liver resection and 9 (42.9%) liver transplantation. Sarcopenia was associated with a higher rate of metastases at diagnosis (49.2% vs 0.0%; p=0.026) and surgical complications (57.1% vs 21.4%, p=0.047). After a median follow-up of 65.1 months (1.7-144.8), 2 patients (28.6%) had tumor relapse in sarcopenic group compared to 1 (7.1%) in non-sarcopenic group. Two patients died in sarcopenic group and 1 in non-sarcopenic group. Median event-free survival (EFS) was lower in sarcopenic group (100.38±25.63vs118.91±11.52 months) as well as overall survival (OS) (101.72±24.86 vs 121.78±8.75 months) with no statistical significance. Five-year EFS was also lower in sarcopenic group (71%vs93%) as well as 5-year OS (71%vs87%). Conclusions: Sarcopenia at diagnosis was associated with a higher rate of metastases and surgical complications in hepatoblastoma. Our data shows the first evidence of its role as a possible poor prognostic factor, influencing survival and risk of relapse.