International Fusion Materials Irradiation Facility—DEMO Oriented Neutron Source (IFMIF-DONES) will be a unique facility dedicated to the irradiation of fusion materials by means of a high neutron flux, with a spectrum comparable to the one expected in the first wall of fusion reactors. Due to the moderate seismicity in southern Spain, the IFMIF-DONES project needs to pay careful attention to the seismic safety and the protection of the machine. The seismic strategy developed for the facility follows the graded approach for seismic design defined by the International Atomic Energy Agency (IAEA), which is consistent with the relatively small radiological/toxicological hazard of the installation and commensurate to its singularity. A comprehensive approach is presented, this encompassing every stage of the seismic design and assessment of the facility. It covers the seismic hazard analysis for the site, including consideration of site effects, the definition of design and beyond design basis earthquakes, the definition of operational earthquakes, the seismic analysis of the Main Building, which will house most of the critical components, and the fragility analysis and seismic margin assessment to demonstrate robustness for the beyond design basis earthquake. This paper provides an overview of the seismic safety strategy now being applied in the IFMIF-DONES Project.