Objective: To investigate the expression and function of miRNA-186-5p in colon cancer. Methods: The miRNA-186-5p expressions in 20 paired specimens of colon cancer tissue and adjacent tissues as well as in normal intestinal epithelial NCM460 cells and different colon cancer cell lines (HCT-116, HRT-18 and HT-29) were determined by qPCR. Then, in HCT-116 cells after transfection with miRNA-186-5p mimics or negative control sequences, the cell proliferation, migration and invasion were measured by CCK-8 assay, plate colony-forming assay, scratch wound-healing assay and Transwell invasion assay, respectively. Results: The miRNA-186-5p expression in colon cancer tissue was significantly lower than that in the adjacent tissue, and in each colon cancer cell line was significantly lower than that in normal intestinal epithelial NCM460 cells (all P<0.05). In HCT-116 cells transacted with miRNA-186-5p mimics compared with HCT-116 cells transfected with negative control sequences, the proliferative ability was decreased, colony forming units were reduced (114.0 vs. 311.7), wound healing rate was lowered (28.7% vs. 77.0%), and the number of invaded cells was decreased (119.3 vs. 259.7), and all the differences had statistical significance (all P<0.05). Conclusion: The miRNA-186-5p expression is down-regulated or absent in colon cancer tissues, and restoring miRNA-186-5p expression can suppress the malignant phenotype in colon cancer cells. So it is suggested that miRNA-186-5p may play an anti-cancer role in colon cancer cells.