Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is significantly upregulated in glioblastoma (GBM) and plays a crucial role in cell apoptosis and drug resistance. Micheliolide (MCL) is a natural product with a variety of antitumour activities, and the fumarate salt form of dimethylamino MCL (DMAMCL: commercial name ACT001) has been tested in clinical trials for recurrent GBM. Our previous work has revealed that MCL/DMAMCL could suppress the proliferation of GBM cells by rewiring aerobic glycolysis. Herein, we demonstrated that MCL directly targets GAPDH through covalent binding to the cysteine 247 (Cys247) residue. Intriguingly, MCL does not affect the enzymatic activity of GAPDH but facilitates the nuclear translocation of the GAPDH/Siah1 (E3 ligase) complex. Furthermore, MCL/DMAMCL can exacerbate temozolomide (TMZ)-induced DNA damage. This treatment synergistically induced GBM cell death and suppressed tumour growth in a GBM xenograft mouse model. Collectively, our results reveal that MCL triggers non-glycolysis-related functions of GAPDH and that MCL promotes GBM cell death, especially when combined with TMZ, thus providing a novel strategy for clinical GBM treatment.