The NRF2 transcription factor controls a cell stress program that is implicated in cancer and there is great interest in targeting NRF2 for therapy. We show that NRF2 activity depends on Fructosamine-3-kinase (FN3K)—a kinase that triggers protein de-glycation. In its absence, NRF2 is extensively glycated, unstable, and defective at binding to small MAF proteins and transcriptional activation. Moreover, the development of hepatocellular carcinoma triggered by MYC and Keap1 inactivation depends on FN3K in vivo. N-acetyl cysteine treatment partially rescues the effects of FN3K loss on NRF2 driven tumor phenotypes indicating a key role for NRF2-mediated redox balance. Mass spectrometry reveals that other proteins undergo FN3K-sensitive glycation, including translation factors, heat shock proteins, and histones. How glycation affects their functions remains to be defined. In summary, our study reveals a surprising role for the glycation of cellular proteins and implicates FN3K as targetable modulator of NRF2 activity in cancer. Display omitted •Glycation is an important mark on intracellular proteins•Glycation and de-glycation regulate the oncogenic transcription factor NRF2•NRF2-driven cancers depend on Fructosamine-3-kinase to de-glycate NRF2 in vivo•Proteomics reveals glycation of several cellular proteins and metabolic enzymes Fructosamine-3-kinase promotes hepatocellular carcinoma by mediating deglycation of NRF2, a protein modification process previously understudied for cellular proteins.