<p>Transcription factor EB (TFEB) is a master regulator of lysosomal biogenesis and cellular clearance pathways. TFEB activity is tightly controlled by multiple post-translational mechanisms, but the exact molecular mechanism controlling its stability has remained elusive. Here, we identify the IκB kinase (IKK) complex as a key regulator of TFEB protein stability through a phosphorylation–ubiquitination cascade. A high-content kinase inhibitor screen reveals that IKK inhibition increases TFEB protein levels, and genetic ablation of IKK components increases TFEB stability, upregulates lysosomal genes, and enhances lysosomal biogenesis and degradative capacity. Mechanistically, we show that IKK phosphorylates TFEB on a cluster of serine residues (⁴²³SPFPSLS⁴²⁹), generating a phosphodegron recognized by the E3 ligase β-TrCP2, which in turn targets TFEB for proteasomal degradation via ubiquitination of adjacent lysine residues (K430 and K431). Mutation of either the phosphosites or the ubiquitination sites stabilizes TFEB without impairing its ability to translocate to the nucleus, activate target gene expression, or promote tau clearance in a cell model of tauopathy. These findings establish IKK–β-TrCP2 as a core regulatory axis controlling TFEB protein turnover and levels and reveal a mechanistically distinct layer of TFEB regulation that may be leveraged to enhance lysosomal function in disease contexts.</p>