We investigated the ability of the ascorbic acid (AA) and menadione (MD) combination, the well‐known reactive oxidative species‐ (ROS‐) generating system, to induce autophagy in human U251 glioblastoma cells. A combination of AA and MD (AA+MD), in contrast to single treatments, induced necrosis‐like cell death mediated by mitochondrial membrane depolarization and extremely high oxidative stress. AA+MD, and to a lesser extent MD alone, prompted the appearance of autophagy markers such as autophagic vacuoles, autophagosome‐associated LC3‐II protein, degradation of p62, and increased expression of beclin‐1. While both MD and AA+MD increased phosphorylation of AMP‐activated protein kinase (AMPK), the well‐known autophagy promotor, only the combined treatment affected its downstream targets, mechanistic target of rapamycin complex 1 (mTORC1), Unc 51‐like kinase 1 (ULK1), and increased the expression of several autophagy‐related genes. Antioxidant N‐acetyl cysteine reduced both MD‐ and AA+MD‐induced autophagy, as well as changes in AMPK/mTORC1/ULK1 activity and cell death triggered by the drug combination. Pharmacological and genetic autophagy silencing abolished the toxicity of AA+MD, while autophagy upregulation enhanced the toxicity of both AA+MD and MD. Therefore, by upregulating oxidative stress, inhibiting mTORC1, and activating ULK1, AA converts MD‐induced AMPK‐dependent autophagy from nontoxic to cytotoxic. These results suggest that AA+MD or MD treatment in combination with autophagy inducers could be further investigated as a novel approach for glioblastoma therapy.