Evodiamine (1), a biologically active alkaloid isolated from Evodia rutaecarpa (known in Chinese as Wu-Chu-Yu), has antioxidant, anti-inflammatory, and anticancer activities. It has recently been demonstrated that the cytotoxic activities of 1 might be due to its ability to inhibit cell growth and induce apoptosis. In this study, we investigated the effects of 1 on growth and apoptosis in COLO-205 cells by MTT assay, fluorescence microscopy, transmission electron microscopy, DNA fragmentation assay, flow cytometry, immunohistochemical analysis, Western blotting, and caspase-3 activity assay. Our data revealed that 1 could significantly inhibit COLO-205 cell proliferation in a dose-dependent manner, and 1-treated COLO-205 cells displayed typical morphological apoptotic characteristics and formation of DNA ladders in agarose gel electrophoresis. The COLO-205 cell cycle was arrested in G(2)/M phase by 1. Meanwhile, 1 increased the expression of Bax and p53, decreased the expression of Bcl-2, lowered the mitochondrial transmembrane potential, and induced the activation of caspase-3. These activities may contribute to the anticarcinogenic action of 1.