Colorectal cancer is one of the leading causes of death in the world. Plant-derived products have proven to be valuable sources for discovery and development of unique anticancer drugs. In this study, the inhibitory effects of ethanolic extract of Melia toosendan fruit (EMTF), a traditional medicine in the Chinese Pharmacopeia were evaluated in vitro and in vivo against colon cancer. Human colon cancer cells SW480 and murine colorectal adenocarcinoma cells CT26 were used to investigate cell proliferation. The results showed that EMTF inhibited cell proliferation of SW480 and CT26 by promoting apoptosis as indicated by nuclear chromatin condensation and DNA fragmentation. Through increasing mitochondrial membrane permeability and cytochrome c release from mitochondria, EMTF induced caspase-9 activity which further activated caspase-3 and poly(ADP-ribose) polymerase cleavage, leading the tumor cells to apoptosis. The in vivo results confirmed reduction of tumor volume and apoptotic effects and the side effects were not induced by EMTF. Therefore, EMTF may be an effective chemotherapeutic agent for colon cancer treatment.