New cisplatin-stitched polysaccharide vesicular nanocarrier is developed for combination therapy of three clinical important antagonistic drugs together to accomplish synergistic cancer therapy in breast cancer treatment. Carboxylic functionalized dextran was tailor-made for the chemical conjugation of cisplatin, and a renewable hydrophobic unit was anchored in the backbone to interdigitize the chains to self-assemble as cisplatin-stitched polysaccharide nanovesicles. Water-soluble DNA-intercalating drug doxorubicin HCl (DOX) and water insoluble topoisomerase type I inhibitor drug camptothecin (CPT) were encapsulated in these vesicles to produce dual or triple drug-loaded vesicular nanocarrier. This unique cisplatin; DOX and CPT triple drug-loaded dextran vesicles were stable in aqueous medium, and the vesicular geometry acted as a shield for Pt-polymer drug conjugate against glutathione (GSH) detoxification under physiological conditions. Lysosomal enzymes ruptured the nanovesicle exclusively at the intracellular compartments to deliver the combination of all three drugs simultaneously to maximize the therapeutic efficacies.. In vitro cytotoxicity studies revealed that free cisplatin was highly detoxified by the GSH in breast cancer cells, whereas the enhanced stability of Pt-stitched dextran vesicle against GSH facilitated similar to 99% cell killing in breast cancer cells. Combination therapy studies revealed that the free cisplatin, DOX, and CPT were found to be antagonistic to each other. Dual drug-loaded vesicles exhibited synergistic cancer cell killing while delivering these antagonistic drugs from a dextran vesicular platform. Remarkable synergistic cell killing was accomplished in cisplatin, DOX, and CPT triple drug-loaded vesicles at nanogram concentrations in breast cancer cells. The internalization of drugs and cellular uptake were confirmed by confocal microscope and flow cytometry analysis. The drugs were taken by the cancer cells in large amounts while delivering them from dextran vesicles compared to their free form. These spectacular results opened new opportunities for synergistic cancer therapy for GSH-overexpressed breast cancer using triple drug-loaded polysaccharide vesicular nanocarriers.