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Summary β-Catenin-dependent WNT signal transduction governs development, tissue homeostasis, and a vast array of human diseases. Signal propagation through a WNT-Frizzled/LRP receptor complex requires proteins necessary for clathrin-mediated endocytosis (CME). Paradoxically, CME also negatively regulates WNT signaling through internalization and degradation of the receptor complex. Here, using a gain-of-function screen of the human kinome, we report that the AP2 associated kinase 1 (AAK1), a known CME enhancer, inhibits WNT signaling. Reciprocally, AAK1 genetic silencing or its pharmacological inhibition using a potent and selective inhibitor activates WNT signaling. Mechanistically, we show that AAK1 promotes clearance of LRP6 from the plasma membrane to suppress the WNT pathway. Time-course experiments support a transcription-uncoupled, WNT-driven negative feedback loop; prolonged WNT treatment drives AAK1-dependent phosphorylation of AP2M1, clathrin-coated pit maturation, and endocytosis of LRP6. We propose that, following WNT receptor activation, increased AAK1 function and CME limits WNT signaling longevity. Graphical Abstract Highlights • Gain-of-function kinome screen identifies AAK1 as a repressor of WNT signaling • AAK1 promotes clathrin-mediated endocytosis of LRP6 • Selective AAK1 inhibitor stabilizes β-catenin and activates WNT signaling • WNT induces AAK1-dependent phosphorylation of AP2M1 and LRP6 endocytosis WNT signal transduction is essential for normal development and contributes to many human diseases. Agajanian et al. used a kinase gain-of-function screen to show that WNT activates the AAK1 kinase to promote clathrin-mediated endocytosis of the WNT receptor. This work identifies an AAK-driven negative feedback loop that downregulates WNT signaling. [ABSTRACT FROM AUTHOR]