BACKGROUND Colorectal cancer is one of the leading causes of death in China, and the development of effective drugs is urgently needed. Here, we report on Paeoniflorin (PF), a product isolated from the roots of the peony plant, as a possible candidate because of its anti-tumor effects on epithelial-to-mesenchymal transition (EMT) of PF in human colorectal cancer (CRC). MATERIAL AND METHODS Cell proliferation, wound healing, and Transwell assays were used to analyze the effects of PF on in vitro cell migration and invasion of HCT116 and SW480, 2 colorectal cancer cell lines. The tumor xenograft model was used to verify the anti-metastasis effects of PF in vivo. The RNA and protein levels of epithelia-cadherin (E-cadherin), Vimentin, and histone deacetylase2 (HDAC2) were measured by qPCR and Western blot analysis to explore the mechanism involved. RESULTS Our results showed that PF inhibited colorectal cancer cell migration and invasion and suppressed the metastatic potential of the cancer cells in vivo. Moreover, PF significantly decreased the expression of HDAC2 and Vimentin, while increasing the expression of E-cadherin. CONCLUSIONS These results suggest that PF inhibits colorectal cancer cell migration and invasion ability and reverses the EMT process, through inhibiting the expression of HDAC2, and then affects the expression level of E-cadherin and Vimentin at the cell level. Our results were also verified in the tumor xenograft model. This indicates that PF may be a candidate for colorectal cancer treatment.