N-myristoyltransferase-1 (NMT1) catalyzes protein myristoylation, a lipid modification that is elevated in cancer cells. NMT1 sustains proliferation and/or survival of cancer cells through mechanisms that are not completely understood. We used genetic and pharmacological inhibition of NMT1 to further dissect the role of this enzyme in cancer, and found an unexpected essential role for NMT1 at promoting lysosomal metabolic functions. Lysosomes mediate enzymatic degradation of vesicle cargo, and also serve as functional platforms for mTORC1 activation. We show that NMT1 is required for both lysosomal functions in cancer cells. Inhibition of NMT1 impaired lysosomal degradation leading to autophagy flux blockade, and simultaneously caused the dissociation of mTOR from the surface of lysosomes leading to decreased mTORC1 activation. The regulation of lysosomal metabolic functions by NMT1 was largely mediated through the lysosomal adaptor LAMTOR1. Accordingly, genetic targeting of LAMTOR1 recapitulated most of the lysosomal defects of targeting NMT1, including defective lysosomal degradation. Pharmacological inhibition of NMT1 reduced tumor growth, and tumors from treated animals had increased apoptosis and displayed markers of lysosomal dysfunction. Our findings suggest that compounds targeting NMT1 may have therapeutic benefit in cancer by preventing mTORC1 activation and simultaneously blocking lysosomal degradation, leading to cancer cell death. Myristoylation consists of the transfer of the fatty acid myristic acid to proteins 1 , and is catalyzed in vertebrates by two isoenzymes called N-myristoyltransferases (NMTs): NMT1 2 and NMT2 3. Myristoylation increases the affinity of proteins for plasma and internal cell membranes and modulates protein activity by a number of mechanisms 1,4. NMT1 is essential for early embryonic development 5 , and deletion of both isoenzymes impairs T cell development and activation in mice 6. NMT1 expression is increased in cancer 7 , associates with poor patient outcome 8 , and has been considered as a target for therapeutic intervention 9. Accordingly, NMT1 activity promotes proliferation and survival of ovarian and colon cancer cells 10 , facilitates cancer cells survival through AMPKβ-dependent regulation of mitophagy 8 , promotes Src-dependent cell cycle progression in prostate cancer 11 , and regulates proteostasis 12,13 .