Liver transplantation (LT) is the primary treatment for patients with early-stage hepatocellular carcinoma (HCC). However, the 5-year survival rate after LT remains low for patients with advanced HCC. Recently, combining programmed cell death protein-1 (PD-1) inhibitors with hepatic arterial infusion chemotherapy (HAIC) has achieved promising outcomes in advanced HCC treatment. However, there is a lack of sufficient clinical data demonstrating its effectiveness as a pre-LT down-staging treatment. The current study presented a case of advanced HCC beyond the Milan criteria who underwent LT and achieved a favorable outcome following PD-1 inhibitor combined with FOLFOX-HAIC therapy. Of note, due to treatment-induced tumor necrosis, precise post-treatment tumor size evaluation became challenging. To address this, circulating tumor DNA (ct-DNA) clearance was used as the LT criterion. After three cycles of Pembrolizumab and FOLFOX-HAIC therapy, the patient's serum ctDNA became undetectable and serum α-fetoprotein levels returned to normal. Magnetic resonance imaging results also revealed a significant reduction in liver tumor size post down-staging treatment. Subsequent to LT, serum ctDNA was monitored every two months, consistently yielding diminished results. There were no clinical signs of recurrence 19 months post-LT. These findings suggest that Pembrolizumab in combination with FOLFOX-HAIC may serve as a potential down-staging strategy prior to LT. In addition, ctDNA clearance may be considered a viable biomarker for LT eligibility.