Biliary tract tumors (BTC) account for about 3% of all digestive system tumors, with rising incidence and limited treatment options, particularly for advanced stages, underscoring the need for innovative therapies. This retrospective cohort study evaluated the safety and efficacy of a novel regimen combining hepatic artery infusion chemotherapy with 5-fluorouracil, leucovorin, and oxaliplatin (mFOLFOX-HAIC) alongside lenvatinib and programmed cell death protein-1 (PD-1) inhibitors (mFOLFOX-HAIC+lenvatinib+PD-1i) compared to standard regimens of gemcitabine plus cisplatin, gemcitabine plus S1, or gemcitabine plus oxaliplatin (GC/GS/GEMOX) in advanced BTC patients treated from March 2019 to November 2023. A total of 89 patients were analyzed, with 55 receiving hepatic arterial infusion chemotherapy and 34 receiving the GC/GS/GEMOX regimens. Among these, 23 patients were in the mFOLFOX-HAIC+lenvatinib+PD-1i group, while 24 were in the GC/GS/GEMOX group. The median progression-free survival (mPFS) for the mFOLFOX-HAIC+lenvatinib+PD-1i group was 15 months compared to 6 months for the GC/GS/GEMOX group. Similarly, the median overall survival (mOS) was 20 months for the mFOLFOXHAIC+lenvatinib+PD-1i group versus 13 months for the GC/GS/GEMOX group. The objective response rate (ORR) and disease control rate (DCR) for the mFOLFOX-HAIC+lenvatinib+PD-1i group were 48.5% and 87.0%, respectively, both significantly higher than those observed in the GC/GS/GEMOX group at three months of treatment. The incidence of adverse events (AEs) was similar between the mFOLFOX-HAIC+lenvatinib+PD-1i group and the GC/GS/GEMOX group, at 86.5% and 84.2%, respectively, with no statistically significant difference in complication rates. Overall, mFOLFOX-HAIC+lenvatinib+PD-1i appears to be a safe and well-tolerated treatment for advanced BTC, demonstrating superior mPFS and mOS compared to standard regimens.