Background: Estrogen receptor β (ERβ) is abundantly expressed in colorectal tissue, but its role in colorectal carcinogenesis remains elusive. ER novel co-regulator, proline-, glutamic acid- and leucine-rich protein 1 (PELP1/MNAR) has been characterized, but its expression in colorectal carcinomas has not been investigated.Methods: ERα, ERβ and PELP1/MNAR protein expression were evaluated by immunohistochemistry in colorectal normal mucosa, adenomas and adenocarcinomas from 113 patients with colorectal cancer.Results: ERα expression is extremely rare in colorectal tissue and its expression does not appear to be associated with colorectal carcinogenesis. ERβ and PELP1/MNAR were detected in the nucleus of epithelial, endothelial, inflammatory, smooth muscle cells and myofibroblasts. When intensity of staining was taken into account, the expression of both proteins was significantly increased in epithelial cells of carcinomas compared to normal mucosa. ERβ expression in epithelial cells was correlated with decreased disease progression – free survival. PELP1/MNAR overexpression in epithelial cells was found to be an independent favorable prognostic factor. Additionally, the expression of both proteins was significantly increased in stromal myofibroblasts of carcinomas compared to adenomas and normal mucosa.Conclusion: ERβ and PELP1/MNAR appear to be involved in colorectal tumorigenesis and might have prognostic significance.