The β-catenin gene is a critical component of Wnt signaling pathway. Aberrant activation of Wnt/β-catenin signaling and subsequent upregulation of β-catenin is related to enhancing cell proliferation and developing colon polyps and colon cancer. In the present study, the effect of β-catenin knockdown on the growth and survival of the human colon cancer cell line HT-29 was investigated in vitro. The effect of knockdown of β-catenin on cell proliferation was investigated by MTT assay and colony formation. The cell cycle distribution was investigated by flow cytometry. Apoptosis was measured by nuclear staining and flow cytometry. The change of β-catenin and related proteins were determined by western blotting and immunofluorescence. The results showed that small interfering RNA directed against β-catenin markedly inhibited the expression and nuclear translocation of β-catenin and decreased the expression of known target genes such as cyclin D1 and c-myc; HT-29 cell proliferation was inhibited as indicated by growth reduction, cell cycle arrest in G0/G1 phase, and induction of apoptosis; and the inhibition of cell growth may be associated with switching off cyclin D1 and c-myc expression by small interfering RNA targeted against β-catenin in colon cancer HT-29 cells.