Aspidosperma alkaloids, a subclass of monoterpenoid indole alkaloids rich in the Apocynaceae plants, possess remarkable antitumor activities, but the underlying mechanisms have rarely been reported. In the current project, 11-methoxytabersonine (11-MT), an aspidosperma-type alkaloid isolated from Tabernaemontana bovina, significantly inhibited the viability of two human lung cancer cell lines A549 and H157, and the molecular mechanisms were thus investigated. The results showed that 11-MT killed lung cancer cells via induction of necroptosis in an apoptosis-independent manner. In addition, 11-MT strongly induced autophagy in the two cell lines, which played a protective role against 11-MT-induced necroptosis. Finally, the autophagy caused by 11-MT was found to be via activation of the AMP activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) and the c-Jun N-terminal kinase (JNK) signaling pathways in both cells. Taken together, 11-MT exhibited an antitumor mechanism different from that of previously reported analogues and could have the potential to serve as a lead compound for the development of new chemotherapy for lung cancer.