To elucidate the complex interplay of undifferentiated cancer cells in malignancy, we focus on the crucial mechanisms that maintain the undifferentiated state of cancer stem-like cells, which drive tumor growth and therapy resistance. Here, we identify a protein called dehydrogenase/reductase 13 (DHRS13) that is abundant in undifferentiated glioblastoma cells. DHRS13 is primarily located in the mitochondria and functions as a retinaldehyde reductase, converting all-trans-retinaldehyde to all-trans-retinol with high affinity for NADPH. Mechanistically, DHRS13 prevents glioma stem-like cells from differentiating by blocking retinoic acid signaling, thereby maintaining their undifferentiated state. Remarkably, the depletion of DHRS13 results in mitochondrial reactive oxygen species-driven mitophagy and cell death. Consequently, loss of DHRS13 leads to a significant decrease in tumor initiation and progression. These findings hold promise for the development of strategies that target undifferentiated cancer cells, potentially leading to improved treatment outcomes.