Rsf-1 (HBXAP) was recently reported to be overexpressed in various cancers and associated with the malignant behavior of cancer cells. However, the expression of Rsf-1 and its biological roles in colon cancer have not been reported. The molecular mechanism of Rsf-1 in cancer aggressiveness remains ambiguous. In the present study, we analyzed the expression pattern of Rsf-1 in colon cancer tissues and found that Rsf-1 was overexpressed in 50.4 % of colon cancer specimens. There was a significant association between Rsf-1 overexpression and TNM stage (p = 0.0205), lymph node metastasis (p = 0.0025), and poor differentiation (p = 0.0235). Furthermore, Rsf-1 overexpression correlated with a poor prognosis in colon cancer patients (p = 0.0011). In addition, knockdown of Rsf-1 expression in HT29 and HCT116 cells with high endogenous Rsf-1 expression decrease cell proliferation and colony formation ability. Further analysis showed that Rsf-1 knockdown decreased cyclin E expression and phospho-Rb level. In conclusion, Rsf-1 is overexpressed in colon cancers and contributes to malignant cell growth by cyclin E and phospho-Rb modulation, which makes Rsf-1 a candidate therapeutic target in colon cancer.