Using both mammalian two-hybrid assay in vivo and immunoprecipitation in vitro we found that retinoid X receptor alpha (RXR alpha) directly interacted with beta-catenin and suppressed beta-catenin transcription activity and protein expression in colorectal cancer cells. But, reduction of RXR alpha by small interfering RNA upregulated beta-catenin transcriptional activity and protein expression. However, gain- or loss-expression of beta-catenin did not affect RXR alpha. Therefore, our data provided the first evidence tht RXR alpha directly interacted with beta-catenin and regulated beta-catenin transcription, which provides important information for developing novel strategies in colorectal cancer prevention by targeting RXR alpha-beta-catenin signaling.