Background: Programmed cell death protein-1 inhibitors combined with lenvatinib have become a popular treatment option for patients with unresectable hepatocellular carcinoma. Transarterial chemoembolization combined with programmed cell death protein-1 inhibitors and lenvatinib has also shown preliminary efficacy in the unresectable hepatocellular carcinoma. We conducted this observational, retrospective, cohort study to compare the clinical outcomes and safety of transarterial chemoembolization combined with programmed cell death protein-1 inhibitors plus lenvatinib versus programmed cell death protein-1 inhibitors plus lenvatinib in patients with unresectable hepatocellular carcinoma. Methods: Between November 2019 and November 2021, patients who were diagnosed with unresectable hepatocellular carcinoma and received transarterial chemoembolization combined with programmed cell death protein-1 inhibitors plus lenvatinib or programmed cell death protein-1 inhibitors plus lenvatinib treatment were reviewed for eligibility. The primary endpoints included objective response rate, overall survival, and progression-free survival. The secondary endpoint was the frequency of key adverse events. Results: In total, 105 patients were eligible for the present study, and they were divided into the transarterial chemoembolization combined with programmed cell death protein-1 inhibitors plus lenvatinib group (n = 46) and the programmed cell death protein-1 inhibitors plus lenvatinib group (n = 59). The patient cohort after a one-to-one propensity score matching (n = 86) was also analyzed. The transarterial chemoembolization combined with programmed cell death protein-1 inhibitors plus lenvatinib group had a higher objective response rate both in the patient cohort before propensity score matching (54.3% vs 25.4%, P = .002) and after propensity score matching (55.8% vs 30.2%, P = .017). The patients in the transarterial chemoembolization combined with programmed cell death protein-1 inhibitors plus lenvatinib group had prolonged overall survival (median, 20.5 vs 12.6 months, P = .015) and progression-free survival (median, 10.2 vs 7.4 months, P = .035). For patient cohort- propensity score matching, the overall survival (20.5 vs 12.8 months, P = .013) and progression-free survival (12.1 vs 7.8 months, P = .030) were also significantly better in the transarterial chemoembolization combined with programmed cell death protein-1 inhibitors plus lenvatinib group than in the programmed cell death protein-1 inhibitors plus lenvatinib group. There were no significant differences between the 2 groups concerning adverse reactions caused by immunotherapy and lenvatinib. The adverse reactions caused by transarterial chemoembolization were transient and were quickly reversed. Conclusions: Compared to programmed cell death protein-1 inhibitors plus lenvatinib, transarterial chemoembolization combined with programmed cell death protein-1 inhibitors plus lenvatinib may provide better treatment response and survival benefits for patients with unresectable hepatocellular carcinoma, and the adverse events were manageable.