This study aimed to determine the effect of miR-186-3p and KRT18 interaction on the biological behavior of colon cancer cells. A biotin-microRNA pull-down assay was performed to identify potential miRNAs. qRT-PCR was used to verify the KRT18 and miR-186-3p levels. In addition, Western blotting was used to detect the KRT18 protein levels. The functional connection between KRT18 and miR-186-3p was confirmed using a dual luciferase reporter assay. BrdU incorporation, MTT assay, and flow cytometry were performed to verify the biological function coupled with in vivo assays. A significant decrease in miR-186-3p expression was observed in colon carcinoma tissues and cells. Functionally, overexpression of miR-186-3p displayed an obvious suppressive action on cell proliferation and viability, and a stimulatory action on the apoptotic ability of SW620 and SW480 cells. Conversely, reduced miR-186-3p had a marked stimulatory effect on proliferation and viability, and a suppressive apoptotic effect. Inhibition of tumorigenesis was observed in mice treated with the miR-186-3p agomir. Furthermore, we identified that miR-186-3p regulated KRT18 levels in colon carcinoma, where silenced KRT18 suppressed proliferation and viability and promoted apoptosis. However, the addition of a miR-186-3p inhibitor weakened the effects of si-KRT18. Additionally, the activation of MAPK signaling pathway upon miR-186-3p silencing was antagonized by the combined transfection of si-KRT18 and miR-186-3p inhibitor. miR-186-3p suppresses proliferation and viability, but facilitates apoptosis in colon cancer cells by targeting KRT18 and negatively regulating the MAPK signaling pathway, indicating that the miR-186-3p/KRT18 axis may be a promising therapeutic target for colon carcinoma.