NSUN5, a gene encodes a cytosine-5 RNA methyltransferase, is rarely mentioned in cancers. Our study is the first one to evaluate the role of NSUN5 in the progression of colorectal cancer. Data from TCGA was used to show the different expression of NSUN5 between CRC tumor tissues and adjacent normal ones. The NSUN5 expression in the tissue microarray was detected by immunohistochemistry (IHC). qRT-PCR was conducted for NSUN5 expression examination in CRC cell lines. Cell proliferation was analyzed by the Celigo machine. GESA and correlation analysis were performed to reveal the possible underlying mechanism. The effects of NSUN5 expression on CRC cell behavior in vitro were analyzed by flow cytometry and β-galactosidase staining. The expression of cell-cycle related proteins were evaluated by western blot. Subcutaneously implanted tumor model was carried out for animal experiment. NSUN5 expression was up-regulated in CRC tumor tissues and cells, and associated with advanced tumor stages (III, IV). NSUN5 could promote cell proliferation, trigger cell cycle arrest in vitro and boost tumor growth in vivo. In addition, knockdown of NSUN5 could lead to a higher expression of Rb and a lower expression of CDK4, CDK6, p-Rb and CCNE1, but made no difference on P21, Bcl-2, caspase3 and C-Caspase3 of CRC cells. Taken together, we identify NSUN5 as a promoter in CRC development via cell cycle regulation.