PTEN is a phosphatidylinositol-3,4,5-triphosphate (PIP₃) phospholipid phosphatase that is commonly mutated or silenced in cancer. PTEN's catalytic activity, cellular membrane localization, and stability are orchestrated by a cluster of C-terminal phosphorylation events on Ser380, Thr382, Thr383, and Ser385, but the molecular details of this multifaceted regulation have remained uncertain. Here we use a combination of protein semisynthesis, biochemical analysis, NMR, X-ray crystallography, and computational simulations on human PTEN and its sea squirt homolog VSP to obtain a detailed picture of how the phospho-C-tail belts around PTEN's C2 and phosphatase domains. We also visualize a previously proposed dynamic N-terminal alpha-helix and show it is key for PTEN catalysis but disordered upon phospho-C-tail interaction. This structural model provides a comprehensive framework for how C-tail phosphorylation can impact PTEN's cellular functions.