Background and Aims CNLC stage IIIb hepatocellular carcinoma (HCC) is often accompanied by extrahepatic metastases and carries a poor prognosis. The optimal treatment strategy for these patients remains controversial, and the role of local therapy lacks robust evidence. This study aimed to compare overall survival (OS) between patients receiving combined local and systemic therapy versus systemic therapy alone, and to assess the prognostic impact of oligometastatic status and the cumulative duration of no evidence of disease (NED).Methods A retrospective analysis was conducted on 76 CNLC stage IIIb HCC patients treated at Xiangya Hospital from January 2017 to December 2023. Forty patients received systemic therapy plus local therapy (local therapy group), and 36 received systemic therapy alone (no local therapy group). OS was compared between the two groups. Subgroup analyses were performed for oligometastatic and non-oligometastatic patients to evaluate the benefit of local therapy. In the local therapy group, the correlation between cumulative NED duration and OS was also examined.Results The 1-, 2-, 3-, and 5-year OS rates were 89.0% vs. 66.7%, 64.3% vs. 25.6%, 35.3% vs. 8.7%, and 8.3% vs. 0.0% for the local therapy and no local therapy groups, respectively, with a statistically significant difference (P=0.003). Among oligometastatic patients, the local therapy group had significantly better OS than the no local therapy group (P=0.008), whereas no significant difference was observed in non-oligometastatic patients (P>0.05). Multivariate analysis identified oligometastases as an independent prognostic factor (HR=2.213, P=0.045). In the local therapy group, cumulative NED duration was strongly correlated with OS (r=0.851, P<0.001). Local therapy was well tolerated, with no treatment-related deaths observed.Conclusion For CNLC stage IIIb HCC patients with well-controlled intrahepatic disease, local therapy can significantly prolong survival, particularly in those with oligometastases. Achieving and maintaining NED may represent an important therapeutic goal in this patient population.