Amino acid homeostasis is critical for leukemic cell survival, with the mTOR pathway playing a central role in sensing and responding to nutrient availability. DEPTOR, a component and negative regulator of mTOR complexes, has been extensively studied in solid tumors and multiple myeloma, but its role in acute myeloid leukemia (AML) remains unclear. Here, we identify DEPTOR as a key regulator of leukemia progression through its interaction with KIF11. DEPTOR expression is transcriptionally induced by ATF4 and post-transcriptionally stabilized by MSI2, which binds to DEPTOR mRNA and prevents its degradation. DEPTOR is highly expressed in leukemia stem cells (LSCs) and is associated with poor clinical outcomes. Functionally, DEPTOR loss impairs leukemogenesis in both AML and blast phase chronic myeloid leukemia (bpCML) models, without affecting normal hematopoietic stem cells. Mechanistically, DEPTOR stabilizes KIF11 by preventing its ubiquitination and proteasomal degradation, thereby ensuring proper mTORC1 localization and metabolic adaptation during nutrient stress. Collectively, our findings establish the MSI2/DEPTOR/KIF11 axis as a critical driver of leukemogenesis and a promising therapeutic target for aggressive myeloid leukemias.