Background: The primary means of treating hepatocellular carcinoma (HCC) is radical surgery. However, HCC has a high propensity to recur post-operatively, and no standard adjuvant therapies have been approved. Tumor neoantigens, which are epitopes derived from tumor-specific mutations, may be utilized in personalized vaccines to activate T cell responses. This trial aims to assess the safety and efficacy of personalized neoantigen pulsed autologous dendritic cell vaccine (Neo-DCVac-02) in patients with HCC. Methods: Eligible patients had histologically confirmed high-risk HCC after radical surgery. Upon obtaining the baseline biopsy specimens and PBMCs of appropriate quality for DNA and RNA sequencing, neoantigen prediction, screening, and synthesis were performed. Subsequently, autologous dendritic cells (DCs) were generated and pulsed with neoantigen peptides to produce Neo-DCVac-02.On day 0, patients were treated with cyclophosphamide at a dose of 250 mg/m². The prepared Neo-DCVac-02 vaccine was administered subcutaneously on day 1, followed by GM-CSF administered daily for 5 days. The primary objectives of this study were to evaluate the feasibility and safety/tolerability. Secondary objectives included assessment of immune responses (via vaccine response: IFNγ ELISpot), recurrence-free survival (RFS), and overall survival (OS). Results: A total of 32 patients provided informed consent to initiate the process of personalized neoantigen discovery, of which 26 (81%) met the requirements for successful product selection for clinical manufacturing. And feasibility was shown with 13 patients receiving Neo-DCVac-02. Thirteen patients did not receive neoantigen vaccines (7 for progressive disease,6 for withdrawal of informed consent because of COVID-19). Treatment was well-tolerated with no grade 2+ treatment-related adverse events (TRAEs). The common grade 1TRAEs were neutropenia (8.3%), injection site reactions (75%), rash (16.7%), fatigue (8.3%), and headache (8.3%). The median follow-up to date is 19.30 (14.4-31.9) months, with median RFS and OS not yet reached and a 1-year RFS of 83%. Five of 13 evaluable patients showed elevated antigen-specific T-cell activity by IFNγ ELISpot for more than 50% of neoantigen peptides in Neo-DCVac-02, and persistent cellular responses were noted out to 1 year. Increases in activation/co-stimulatory of T cells seen after treatment with Neo-DCVac-02 revealed by Flow-cytometric analyses, suggest immune priming. Conclusions: These data demonstrate that Neo-DCVac-02 is safe, well tolerated, and able to generate durable antigen-specific lymphocyte immune responses. Early signs of clinical efficacy were observed in HCC patients. Clinical trial information: NCT04147078.