Triple-negative breast cancer (TNBC), one of the grievous types of breast cancer, is extremely harmful to women’s health. Norcantharidin (NCTD), a synthetic demethylated analogue of zebularin, has been reported to exhibit anticancer efficacy. During this study, we discovered that NCTD obviously induced breast cancer MDA-MB-231 cell apoptosis through upregulating the levels of Bax/Bcl-2 and cleaved-PARP/PARP and the expression of cleaved-caspase-9 and cleasved-caspase-3 and downregulating the levels of MCL-1 and pro-caspase-8, ultimately inhibiting MDA-MB-231 cell proliferation. Furthermore, flow cytometry analyses showed that NCTD observably reduced mitochondrial membrane potential and rose mitochondrial ROS. Confocal microscopy showed that autophagic flow was blocked in NCTD-treated cells expressing mCherry-EGFP-LC3. Moreover, NCTD upregulated the levels of LC3-II/LC3-I and mitochondrial translocation of Parkin. Finally, we found that the combination of NCTD with chloroquine (CQ), an inhibitor that breaks the fusion of autophagosomes with lysosomes, exacerbated NCTD-induced MDA-MB-231 cell apoptosis, while the combination of NCTD with 3-methyladenine (3-MA), an inhibitor that blocks the formation of autophagosome, decreased NCTD-induced MDA-MB-231 cell apoptosis. Together, our data suggest that NCTD can induce autophagosome accumulation and cause apoptosis, providing a theoretical basis for the treatment of MDA-MB-231 cells.