For unresectable hepatocellular carcinoma (HCC), nivolumab (anti-programmed death receptor-1 (PD-1)) is used as non-curative interventions. The aim of the study was to focus on the real-world experience of nivolumab applied to patients with HCC. Unresectable HCC patients receiving nivolumab treatments at Taichung Veterans General Hospital, from June 2018 to May 2020, were recruited. Exclusion criteria were Child-Pugh stage C, poor performance status, a lack of compliance or intolerable to drug treatments. The tumor radiological responses and survival outcomes of enrolled patients were collected and analyzed. Among a total of 57 patients, most of them were classified as Child-Pugh stage A (70.2%) and Barcelona Clinic Liver Cancer (BCLC) stage C (66.7%). Nivolumab was given to 14 (24.6%) as the primary-line, and 43 patients (75.4%) as the secondary-line systemic treatments. The mean therapeutic duration was 6.5 months. Objective response rate (ORR) was 24.6%, and disease control rate (DCR) was 42.1%. The overall median progression-free survival (PFS) was 5.8 months (95% confidence interval (CI): 1.1 - 10.6), and overall survival (OS) was 11.5 months (95% CI: 4.3 - 17.8). Immune-related adverse event (IRAE) was 8.8%. Presence of alpha-fetoprotein (AFP) response (a decline in AFP ≥ 10% from baseline) during therapy predicted the tumor radiological response (to objective response: hazard ratio (HR): 4.89, 95% CI: 1.14 - 21.00; to disease control: HR: 4.71, 95% CI: 1.32 - 16.81). Those with tumor radiological responses showed longer PFS and OS. Decline in AFP during therapy has a predicting role on HCC radiological responses to nivolumab. Achieving radiological responses had better survival outcomes.