β-Catenin can play different roles in the cell, including one as a structural protein at cell-cell adherens junctions and another as a transcriptional activator mediating Wnt signal transduction. Plakoglobin (γ-catenin), a close homolog of β-catenin, shares with β-catenin common protein partners and can fulfill some of the same functions. The complexing of catenins with various protein partners is regulated by phosphorylation and by intramolecular interactions. The competition between different catenin partners for binding to catenins mediates the cross-talk between cadherin-based adhesion, catenin-dependent transcription and Wnt signaling. Although plakoglobin differs from β-catenin in its functions and is unable to compensate for defects in Wnt signaling resulting from lack of β-catenin, recent evidence suggests that plakoglobin plays a unique role in Wnt signaling that is different from that of β-catenin. The functional difference between catenins is reflected in their differential involvement in embryonic development and cancer progression.