Wnt/β-catenin signaling has central roles in embryogenesis and human diseases including cancer. A central scheme of the Wnt pathway is to stabilize the transcription coactivator β-catenin by preventing its phosphorylation-dependent degradation. Significant progress has been made toward the understanding of this crucial regulatory pathway, including the protein complex that promotes β-catenin phosphorylation–degradation, and the mechanism by which the extracellular Wnt ligand engages cell surface receptors to inhibit β-catenin phosphorylation–degradation. Here we review some recent discoveries in these two areas, and highlight some crucial questions that remain to be resolved.