Background and Aim(s): Transarterial chemoembolization (TACE) is the main treatment for intermediate-stage hepatocellular carcinoma (HCC), but its suitability varies due to tumor burden and liver function heterogeneity. TACE may worsen liver function in large tumors. This study aims to develop a model to predict one-year mortality in intermediate-stage HCC patients undergoing TACE as first-line therapy. Methods: A retrospective cohort study analyzed data from the Indonesian National Hepatocellular Carcinoma Registry (RINKAS) at Cipto Mangunkusumo and Dharmais Cancer Hospitals (2006–2022). Prognostic factors for one-year mortality were identified using bivariate and multivariate Cox regression. The resulting model was evaluated for discrimination, calibration, and internal validation using AUROC, Hosmer-Lemeshow test, calibration curve, and bootstrapping. Results: Among 538 intermediate-stage HCC patients, 191 received TACE, with a one-year survival rate of 49.8% and a median survival of 362 days. Significant predictors of mortality included ALBI grade 2–3 (HR 1.97; p = 0.003), nodule size ≥11 cm (HR 1.57; p = 0.04), and AFP ≥1000 ng/mL (HR 2.41; p < 0.001). The MANTAP model, based on these variables, stratifies patients into low-risk (score 0–1, mortality 29.6%), moderate-risk (score 2, mortality 52.9%), and high-risk (score 3–4, mortality 75.1%) groups. The model showed acceptable predictive performance (AUROC 0.72), good calibration (Hosmer-Lemeshow p = 0.343), and robust validation. Conclusions: The MANTAP score proposes a simple risk stratification tool for estimating one-year mortality in intermediate-stage HCC patients undergoing TACE as first-line therapy. © 2026