Updated project metadata. Wnt signaling plays a central role in development, adult tissue homeostasis and cancer. Several steps in the canonical Wnt/b-catenin signaling cascade are regulated by ubiquitylation, a protein modification that influences the stability, subcellular localization or protein-protein interactions of target proteins. To identify novel regulators of the Wnt/b-catenin pathway, we performed RNAi screens in C. elegans and human tissue culture cells and identified the HECT domain containing ubiquitin ligase eel-1/Huwe1 as a negative regulator of Wnt signaling. Huwe1 functions cell autonomously in signal-receiving cells and genetically acts upstream of b-catenin. Mechanistically, Huwe1 binds to and ubiquitylates the cytoplasmic Wnt pathway component Dishevelled (Dvl) in a Wnt3a and CK1e dependent manner. Huwe1 mediated ubiquitylation does not target Dvl for degradation. Instead, we found that Huwe1 decreases Dvl signaling by inhibiting Dvl multimerization. We conclude that Huwe1 is part of an evolutionarily conserved negative feedback loop in the Wnt/b-catenin pathway