The combination of electronic and nuclear energy deposition may have a significant effect on the defect production and evolution. In nuclear reactor, the nuclear fuel is exposed to the irradiation of several particles such as the fission fragments (FF). Along their path, the ratio of electronic to nuclear energy loss evolves. To understand the impact of this coupling on the fuel microstructure, single and dual-beam ion irradiations of uranium dioxide (UO2) were carried out. The damage evolution was investigated by Raman spectroscopy analysis correlated with Transmission Electronic Microscopy observations. A significant effect of electronic energy dissipation on defect formation and evolution was found, depending on the electronic energy loss level. With the increase of electronic energy loss, the microstructure evolution is even more pronounced.