BACKGROUND: α-Solanine, the most important and active component of Solanum nigrum, was found to have anti-cancer activity on multiple cancer cells. However, its effects on colorectal cancer (CRC) and associated molecular mechanisms remain to be further elucidated. OBJECTIVE: In this study, we investigated the anti-cancer effects of α-solanine against CRC cells in vitro and in vivo. MATERIALS & METHODS: Cell viability was measured using Cell Counting Kit-8 (CCK-8) assay; cell cycle was analyzed with a Cycletest Plus DNA Reagent Kit; cell apoptosis was detected by flow cytometer; cell migration and invasive ability was determined by Transwell assays; S100P protein expression was also analyzed by western blotting; lentiviral vectors expressing shRNA targeting the S100P gene. RESULTS: We demonstrated that α-solanine inhibited CRC cell (SW480, SW620 and HT-29) growth as well as migration and invasion, induced cell cycle arrest and apoptosis in vitro, and suppressed tumor growth in vivo. Moreover, we observed that S100P expression was downregulated by α-solanine. Overexpression of S100P partially reversed the α-solanine-induced growth inhibition of CRC cells. Conversely, knockdown of S100P by lentiviral-mediated RNAi resulted in significantly promoting the α-solanine-induced growth inhibition. CONCLUSION: These findings suggest that α-solanine is a potential agent for the treatment of CRC, and the anti-tumor effect of α-solanine in the CRC cells may be mediated at least partly by the downregulation of S100P.