Colorectal cancer (CRC) is the second most common cancer-related deaths throughout the world. Ferroptosis is a recently regulated form of cell death, lately gains attention. MicroRNA-15a-3p (miR-15a-3p) plays a regulatory role in various kinds of cancers. However, the role of miR-15a-3p in cellular ferroptosis is still unclear. Here, we aimed to clarify whether miR-15a-3p could regulate the ferroptosis of CRC. Here we identified miR-15a-3p positively regulates ferroptosis via directly targeting glutathione peroxidase glutathione peroxidase 4 (GPX4) in CRC. Overexpression of miR-15a-3p repressed GPX4 through binding to the 3′-untranslated region of GPX4, resulting in increased reactive oxygen species level, intracellular Fe2+ level, and malondialdehyde accumulation in vitro and in vivo. Correspondingly, suppression of miR-15a-3p reduced the sensitivity of CRC cells to erastin and GPX4. Taken together, these data demonstrate that miR-15a-3p regulates ferroptosis through targeting GPX4 in CRC cells, illustrating the novel role of microRNA in ferroptosis.