In the absence of Wnt activation, cytosolic b-catenin is degraded through GSK3/CK1-mediated phosphorylation at the N terminus.Here, we show that, upon Wnt activation, the stability of nuclear b-catenin is regulated via methylation/demethylation.The protein lysine demethylases Kdm2a and Kdm2b regulate the turnover of non-phosphorylated b-catenin specifically within the nucleus via direct interaction with the fourth and fifth armadillo repeats.