Cisplatin (DDP) remains a standard therapy for triple-negative breast cancer (TNBC), yet intrinsic or acquired resistance often limits its efficacy; here, we report that Ramulus Mori alkaloids (SZ-A), an approved botanical α-glucosidase inhibitors, synergize with DDP to suppress TNBC progression in vitro and in vivo by driving PLA2G2A-dependent ceramide accumulation. Combining SZ-A with DDP synergistically inhibits viability, clonogenicity, migration, and invasion, induces S-phase arrest and apoptosis, and attenuates tumor growth in xenograft models. Mechanistically, SZ-A directly binds to and stabilizes PLA2G2A, blocking its autophagic-lysosomal degradation, leading to accumulated PLA2G2A that suppresses fatty acid oxidation and triggers ceramide accrual via ADIPOR2 inhibition. Genetic ablation of PLA2G2A abrogates these effects. DDP further enhances SZ-A-induced PLA2G2A upregulation and ceramide accumulation, resulting amplified cytotoxicity. Our findings reveal SZ-A as a chemosensitizing agent that enhances the efficacy of DDP in TNBC.