In addition to its role in cell adhesion, β-catenin is an important signaling molecule in the Wnt/Wingless signaling pathway. Recent studies have indicated that β-catenin is stabilized by hypertrophic stimuli and may regulate cardiac hypertrophic responses. To explore the role and requirement of β-catenin in cardiac development and hypertrophy, we deleted the β-catenin gene specifically in cardiac myocytes by crossing loxP-floxed β-catenin mice with transgenic mice expressing a Cre recombinase under the control of the α-myosin heavy chain promoter. No homozygous β-catenin-deleted mice were born alive and died before embryonic day 14.5, indicating significant and irreplaceable roles of β-catenin in embryonic heart development. Heterozygous β-catenin-deleted mice, however, demonstrated no structural and functional abnormality. The response of heterozygous β-catenin-deleted mice to transverse aortic constriction, however, was significantly attenuated with decreased heart weight and heart weight/body weight ratio compared to controls with intact β-catenin genes. Hemodynamic analysis revealed that there was no difference in cardiac function between wild-type and heterozygous β-catenin-deleted mice. On the other hand, the expression of fetal genes, β-myosin heavy chain, atrial and brain natriuretic peptides was significantly higher in heterozygous β-catenin-deleted mice when compared to wild-type β-catenin mice. These results suggest that the cytoplasmic level of β-catenin modulates hypertrophic response and fetal gene reprogramming after pressure overload.