Colorectal cancer is one of the most common cancers in men and women in the world. Previous molecular studies have revealed that deregulation of the ß-catenin signaling pathway plays a crucial role in the progression of colorectal cancer. Therefore, modulation of the ß-catenin pathway offers a strategy to control colorectal cancer progression. The medicinal mushroom Ganoderma lucidum (GL) is a rich source of triterpenes with anticancer properties. Here, we show that ganodermanontriol (GNDT), a purified triterpene from GL, inhibited proliferation of HCT-116 and HT-29 colon cancer cells without a significant effect on cell viability. Moreover, GNDT inhibited transcriptional activity of ß-catenin and protein expression of its target gene cyclin D1 in a dose-dependent manner. A marked inhibition effect was also seen on Cdk-4 and PCNA expression, whereas expression of Cdk-2, p21 and cyclin E was not affected by the GNDT treatment. In addition, GNDT caused a dose-dependent increase in protein expression of E-cadherin and ß-catenin in HT-29 cells. Finally, GNDT suppressed tumor growth in a xenograft model of human colon adenocarcinoma cells HT-29 implanted in nude mice without any side-effects and inhibited expression of cyclin D1 in tumors. In conclusion, our data suggest that ganodermanontriol might be a potential chemotherapeutic agent for the treatment of cancer.